[Published July 1]

Generally Covariant Maxwell Theory for Media with a Local Response: Progress since 2000

Friedrich W. Hehl

Room: BChair: Ari Sihvola

- 09:40 Generally Covariant Maxwell Theory for Media with a Local Response: Progress since 2000 (Plenary)
- In the recent decades, it became more and more popular for engineers, physicists, and mathematicians alike to put the Maxwell equations into a generally covariant form. This is particularly useful for understanding the fundamental structure of electrodynamics (conservation of electric charge and magnetic flux). Moreover, it is ideally suited for applying it to media with local (and mainly linear) response behavior. We try to collect the new knowledge that grew out of this development. We would like to ask the participants of EMTS 2016 to inform us of work that we may have overlooked in our review.

Conveners: Matteo Pastorino and Lianlin Li

Room: BChairs: Matteo Pastorino, Lianlin Li

- 11:00 Experimental Validation of Radio Frequency Tomography for an Inhomogeneous Medium (Invited)
- Experimental tests to validate Radio Frequency Tomography (RFT) in the case of an inhomogeneous scenario are reported in this work. The experiments dealt with the imaging of objects buried in a box surrounded by air and filled with sand or gravel. RFT is based on the linear model provided by Born approximation and assumes that multiple transmitters and receivers surround the structure under investigation. The model here adopted accounts for the Green's function of the inhomogeneous medium, which is evaluated numerically by a commercial computational electromagnetic software based on the Method of Moments. Reconstruction results highlight the performance and practical limitations of the RFT approach.
- 11:20 A Combined Approach for Shape Reconstruction from Under-sampled Data (Invited)
- A combined Migration-MUSIC approach is adopted to deal with the inverse problem of reconstructing the shape of strong scatterers composed of elementary shapes and embedded within an electrically large investigation domain from under-sampled backscattered field data. The scatterers are deployed over a metallic plane, which mimics the ground floor, as in SAR scenarios. In order to mitigate aliasing, migration images obtained by using disjoint available frequency bands are combined in an interferometric way. Next as each elementary shape is characterized by a small amount of parameters, a MUSIC algorithm is employed to reconstruct them separately.
- 11:40 Experimental Analysis of Dielectric Structures with a Two-Step Electromagnetic Imaging Method (Invited)
- A novel two-step electromagnetic imaging method, suitable for the analysis of hidden inclusions in dielectric structures, is reported in this paper. In particular, two distinct steps compose the present technique. The first one extracts from the raw data an estimation of the scattered field due to the inclusions, and provides a first qualitative reconstruction of the structure under test. This information is then exploited by the second step, in which a quantitative inexact-Newton inversion approach retrieves a map of the dielectric characteristics of the examined region. Experimental data obtained with a tomograph prototype are used to validate the proposed inversion scheme.
- 12:00 Multi-Resolution Approaches for GPR-Data Inversion (Invited)
- In this work, an innovative approach for GPR imaging is presented. The proposed methodology exploits an iterative multi-resolution scheme (i.e., the IMSA) in order to reduce the overall ratio between problem unknowns and informative data, while processes multi-frequency (MF) components of the measured GPR spectrum through a customized particle swarm optimization (PSO) in order to obtain robust and accurate images of the buried domain. A preliminary numerical example is provided, as well, to show both the effectiveness of the MF-IMSA-PSO and its advantages over its deterministic (local search-based) implementation.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChairs: Kazuya Kobayashi, Yury Shestopalov

- 11:00 Nonlinear Guided Electromagnetic Waves in a Layer: Revisiting an Old Problem and New Results (Invited)
- It is shown that for transverse-electric (TE) waves an open plane waveguide filled with a nonlinear medium of Kerr type supports two different physically interesting guided regimes in the focusing case. One of them has been studied in [Phys. Rev. A 91, 013840 (2015)], for the other one we could not find any record in the literature; in each of the regimes there exists an infinite number of guided waves. In the latter case the corresponding linear problem has no solutions (this case can be applied for negative permittivities). It is also shown that in the defocusing case only one regime arises with a finite number of guided waves; in this case all the solutions have linear counterparts (an infinite number of guided waves exist only in the focusing cases). In addition, it is demonstrated that open and shielded plane waveguides filled with Kerr medium have qualitatively different properties due to the nonlinearity.
- 11:20 Ellipticity of the Electric Field Integral Equation in a Problem of Diffraction by a Partially Shielded Body (Invited)
- Problem of diffraction of electromagnetic waves on a 3D inhomogeneous anisotropic dielectric partially shielded body considered. The problem is reduced to a system of singular integro-differential equations. The operator of the system is treated as a matrix pseudodifferential operator (ΨDO) in Sobolev spaces. Using pseudodifferential operators calculus, ellipticity of the operator of the problem is proved.
- 11:40 Analysis of the TM Plane Wave Scattering from a Dielectric Grating by the Perturbation Method (Invited)
- The scattering of a TM plane wave by a dielectric grating is treated by the perturbation method and the diffraction amplitudes are analytically derived. By comparing with the results obtained by the numerical method it is shown that the properties of the high order diffraction amplitudes can be fairly described by the perturbation solution.
- 12:00 Electromagnetic Time Reversal: What does it Imply? (Invited)
- The main goal of this paper is to explain the definition of the term Time-Reversal in Electrical engineering in general, and in electromagnetics for wireless communications to be specific. First, the goal will be to illustrate its claimed capabilities. Some problems with the application of time reversal in electromagnetics will be discussed both theoretically and practically. All of the time reversal papers talk about reciprocal networks, so the fact of the non-reciprocity of a single-antenna system in time domain (the way we generally interpret it) proves from a theoretical point of view that there is a problem with how we interpret time reversal in electromagnetics. Finally, experimental result is shown where time reversal is used in a wireless system. The exact capabilities of time reversal in electrical engineering are exposed.

Room: D

Chairs: Sergei Tretyakov, Henrik Wallén

- 11:00 Narrow-Band and Dual-Band Metamaterial Absorbers in the THz Regime
- In this paper, we consider the analysis and design of narrow-band and dual-band metamaterial absorbers in the THz regime. We observe a broadening of the angular response obtained through absorbers backed by a conducting ground plane and we apply a homogenization technique to calculate the effective electric and magnetic properties of the structures.
- 11:20 Exceptional Points of Degeneracy in Coupled-Mode Periodic Structures
- We investigate the modal characteristics of coupled waveguides in which the supported eigenmodes coalesce; the condition we refer to as an exceptional point of degeneracy (EPD). In particular, we study different orders of EPD that can be manifested in coupled waveguides, and demonstrate how to realize a second, third, and fourth order degeneracies in the dispersion diagram of the supported eigenmodes. In addition, we illustrate the deterioration of the EPD by incorporating losses and we also investigate the prospects of gain/loss balance and how it is related to realizing an EPD. Such scheme is often attributed to a PT-symmetry under some conditions in gain/loss balanced resonators, however here we generalize it to coupled waveguides exhibiting EPDs, and explore its properties using coupled transmission line approach accounting for loss and gain, not satisfying necessarily the parity symmetry. Our proposed framework can be utilized in various applications including traveling wave tubes, lasers, sensors, pulse compressions, switches and oscillators.
- 11:40 Dual Topological Transition in Polaritonic Wire Media and Its Radiative Implications
- Here, theoretically we uncover two topological transitions of the wave dispersion at midinfrared frequencies in a wire medium formed by lithium tantalate nanowires. We show while one transition is fixed at one certain frequency, the other transition happening at lower frequency can be blue shifted which enables to achieve a broadband enhancement of emission for an infrared emitter embedded into the medium.
- 12:00 Analysis of Corrugated Waveguides using a Periodic-Asymptotic Boundary Conditions Approach
- Periodic-Asymptotic Boundary Conditions (PABCs) are introduced to analyze corrugated rectangular waveguide. The obtained dispersion characteristics show that the conventional Asymptotic Corrugation Boundary Conditions (ACBCs) have notable inaccuracies in predicting the dispersion characteristics, especially the left-hand propagation region. The derived expressions extend the validity of asymptotic boundary conditions in cases where the period is comparable to the wavelength and generally, improve the accuracy of the dispersion characteristics as they incorporate the effect of the high-order Floquet harmonics.

Conveners: Stefano Maci and Timor Melamed

Room: EChairs: Stefano Maci, Timor Melamed

- 11:00 Diverging and Converging Beam Diffraction by Wedges and Cones
- The complex source (CS) approach has long been used to obtain exact and approximate solutions for problems of beam-waves diffraction. However, the straightforward CS formulation may be applied only when the incident beam is diverging as it hits the scatterer, but not when it is converging. The present paper extends the CS method in the context of beam diffraction by wedges and cones, and present somewhat surprising rules for modifying the CS model so that it can addresses both the diverging incident beam (DIB) and the converging incident beam (CIB) cases. Using these models we demonstrate the different phenomenologies associated with each case.
- 11:20 A Uniform Geometrical Theory of Diffraction for the Scattering from Quasi Periodic Finite Planar Arrays Excited by a Nearby Antenna
- This paper presents a uniform geometrical theory of diffraction (UTD) for describing the electromagnetic (EM) scattering from finite, quasi periodic, planar arrays illuminated by incident spherical waves. It is applied here to analyze the scattering by a finite frequency selective surface (FSS), and by a finite reflectarray, respectively when they are excited by a nearby antenna. The UTD yields not only a relatively simple solution to these problems, but it also lends physical insights into the scattering mechanisms via Floquet modal rays arising from the interior points, and diffracted rays arising from the truncation boundaries, respectively, of such finite structures. Numerical examples are shown to validate the UTD analysis.
- 11:40 Gaussian Beams for Quasi-Optical-Systems: Modeling Dichroic Surfaces near a Zero of Transmission or Reflection
- Gaussian-beam based methods are well-known for modeling quasi-optical systems constituted by mirrors, lenses, and horn antennas. In this article, a solution is proposed to include dichroic surfaces while maintaining the Gaussian-beam formulation. Special attention is devoted to the case where the dichroic surface response presents a zero near the angle of incidence. Numerical experiments are led on a dielectric slab to show the efficiency of the method.
- 12:00 Evolutionary Algorithms Applications for Inverse Scattering using Gaussian Beams
- In this work we attempt to overcome the two main limitations of the generic inverse scattering problem, namely the size problem and the ill-posed nature of the problem at hand. We use a solver that is based on the discrete (frame-based) Gaussian beam summation method and apply it for the special case of a smoothly varying inhomogeneous medium. In order to overcome the need to perform simplifying approximations for the propagating medium, we use evolutionary algorithms for the optimization scheme. Such algorithms can overcome the ill-posed nature of the inverse scattering problem, while maintaining a reasonable calculation load. Reconstruction results for several configurations are presented.

Conveners: Andrey Osipov, Piergiorgio Uslenghi and Paul Smith

Room: BChairs: Andrey Osipov, Piergiorgio L.E. Uslenghi

- 13:40 Diffraction by an Impedance Cone and Weyl-Van der Pol Phenomenon in Acoustics and Electromagnetism (Invited)
- The report deals with the asymptotic description of the diffraction pattern which is analogous to the classical Weyl-Van der Pol phenomenon (the Weyl-Van der Pol formula). The latter arises in the problem of diffraction of waves generated by a source located near an impedance plane. The incident wave illuminates a circular impedance cone. The singular point of the cone's boundary (the vertex of the cone) plays the role of an imaginary source giving rise to the specific boundary layer in some vicinity of the corresponding impedance surface provided the surface impedance is relatively small. From the mathematical point of view the description of the phenomenon is given by means of the far field asymptotics for the Sommerfeld integral representations of the scattered field. For the small impedance of the scattering surface the singularities describing the surface wave, which propagates from the the vertex along the impedance surface, may be located in a neighborhood of the saddle points. The latter are responsible for the spherical wave from the vertex of the cone. As a result, the asymptotics of the Sommerfeld integral are uniformly represented by a parabolic cylinder type function (the generalised Fresnel integral) for the cone problem.
- 14:00 High-Frequency Asymptotics for Diffraction by a Strongly Elongated Canonical Object (Invited)
- An asymptotic approach to high-frequency diffraction which yields uniform approximations with respect to the rate of elongation of the body is discussed in this work. The method is restricted in its application to shapes that are rotationally symmetric and are well approximated by second-order curves. Diffraction by a strongly elongated spheroid is examined in more detail.
- 14:20 Electromagnetic Scattering by an Array of Parallel Metallic Half-Planes Perpendicularly Truncated by a Metal Plane (Invited)
- A metallic structure consisting of an infinite array of parallel and equally spaced half-planes truncated by a plane perpendicular to their edge is considered. The primary field is a plane electromagnetic wave that propagates in an arbitrary direction with arbitrary polarization. The boundary-value problem is solved analytically, in the phasor domain.
- 14:40 Analysis of Coupled Angular Regions in Spectral Domain (Invited)
- This paper analyses the problem of coupling multiple angular regions in spectral domain by using the generalized Wiener-Hopf technique. The paper introduces also the technique to obtain a solution of the problem by reducing the factorization problem to Fredholm integral equation. We present a test case constituted by two PEC wedges.
- 15:00 Backscattering from Electrically Large Low-Absorption Spheres (Invited)
- Backscattering from electrically large low-absorption spheres cannot be fully explained in the framework of geometrical optics. This paper studies the role of the so-called horizontal branch of poles of the spectra and shows that the residues at these poles can be interpreted as creeping waves propagating in the interior of the sphere on the concave side of the spherical boundary. In contrast to the well-known creeping waves propagating on the convex side of the spherical boundary, which are associated with the vertical branch of poles and rapidly decay with growing electrical size of the sphere, these new waves are much weaker attenuated and may dominate backscattering from electrically large low-absorption spheres. Analytical formulas for the contributions from the poles of the horizontal branch are obtained, and their relation to the irregular pattern (ripple) in scattering cross sections of electrically large low-absorption spheres is suggested.
- 15:20 Porcupic Concentrators and Bulbic Cloaks in Planar Configuration
- This contribution concerns anisotropic elliptic inclusions in a static and uniform excitation field. In particular, the discussion considers anisotropy which is axial in a way that is defined by the elliptic coordinate system. This type of axial anisotropy has been referred to as "radial anisotropy", although other varieties of radial anisotropy do exist for other geometries. In case of an ellipse, there are at least two methods to create radial anisotropy, and the two methods lead to qualitatively different outcomes. The terms "porcupic" and "bulbic" have been used to refer to these two classes of radial anisotropy. The porcupic inclusions are found to exhibit field concentration and the bulbic ones are found to exhibit cloaking. The contribution discusses both types of inclusions first in isolation and then as layered structures.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChairs: Yury Shestopalov, Nikolay Zernov

- 13:40 Plane Wave Propagation in Extreme Magnetoelectric (EME) Medium (Invited)
- EME medium is defined as one with zero permittivity and inverse permeability. Dispersion equations for the plane wave are shown to be cubic and homogeneous or identically satisfied by the wave vector. Various special cases and reflection from a uniaxial EME medium interface are considered.
- 14:00 General Approach to the Synthesis of Perfectly Refractive Metasurfaces (Invited)
- In this presentation we will introduce and discuss a general approach to the synthesis of metasurfaces for full control of reflected and transmitted fields. The method is based on the use of an equivalent Z-matrix which connects the tangential field components at the two sides on the metasurface. Finding the impedance matrix components, we are able to understand what physical properties of metasurface are needed in order to realize the desired response. Furthermore, we can find the required polarizabilities and/or susceptibilities of the metasurface unit cells and design the cell structures. In particular, we will discuss metasurfaces for perfect refraction into an arbitrary direction, explain possible alternative physical realizations and reveal the crucial role of bianisotropic coupling for design of perfectly matched metasurfaces for transmission control.
- 14:20 The Techniques for Modeling the Effects of High-Frequency Wave Field Strong Scintillations on the Transionospheric Paths of Propagation (Invited)
- The analytical technique and its numerical realizations are presented allowing for studying different regimes of the high frequency wave field strong scintillation, which may be formed when propagating in the stochastic transionospheric channel.
- 14:40 Guaranteed Estimation of Solutions to Transmission Problems for Helmholtz Equation with Uncertain Data From Their Indirect Noisy Observations (Invited)
- We investigate the estimation problems of linear functionals from solutions to transmission problems for Helmholtz equation with inexact data. The right-hand sides of equations entering the statements of transmission problems and the statistical characteristics of observations errors are supposed to be unknown and belonging to the certain sets. It is shown that the linear mean square estimates of the above- mentioned functionals and estimation errors are expressed via solutions to the systems of transmission problems of the special type.
- 15:00 Accurate Boundary Extraction and Dielectric Constant Estimation Method for UWB Internal Imaging Radar (Invited)
- Microwave ultra-wideband (UWB) radar systems have numerous advantages for high range resolution and an ability to penetrate dielectric objects. Internal imaging of dielectric objects by UWB radar is a promising nondestructive method of testing aging roads and bridges and a noninvasive technique for medical diagnoses or human vital sign detection. We have already developed an original method called as range points migration (RPM), which achieves accurate and highresolution imaging for target with continuous boundary shape. In this paper, we introduce the novel method for extracting double-layered dielectric object by using RPM or Envelope based approaches, where a dielectric constant of surrounding medium is simultaneously determined. The results obtained from the numerical simulation and experiment assuming concrete objects, demonstrate the effectiveness of our proposed method.
- 15:20 Numerical Technique for Wireless Communication System with High Speed Movement (Invited)
- Numerical technique for the analysis of EM field with high speed moving dielectric body by using FDTD method with Overset Grid Generation method considering Lorentz transformation is presented. The characteristic of EM field when incident wave hits the moving dielectric body with high velocity value are analyzed. The accuracy of the proposed technique is validated. Good agreements are obtained between numerical results and theoretical results. The development of this numerical technique will give a great impact for many areas, particularly for the future high speed mobile communication systems used in transportation and aerial radar systems to detect the high speed motion of a moving boundary.

Conveners: Sembiam Rengarajan and Yahya Rahmat-Samii

Room: DChairs: Sembiam R. Rengarajan, Jari Holopainen

- 13:40 New Antennas for Space Applications (Invited)
- Metasurfaces (MTSs) are versatile and technologically advanced new materials, which have proven their capability to be successfully employed for constituting variable impedance plane and enabling precisely controlled radiation from equivalent apertures for antenna applications. Among the several requirements that can be desired in Space Communications environment the possibility to obtain shaped beam is one of the most demanding features and in this framework MTS antennas assume a key role. In this work two new designs of shaped beam antenna configurations are presented. These implement a low-complexity data-downlink aperture for Ka-band LEO missions and, in the second example, a printed MTS is applied for pattern shaping of a Ku-band horn for global Earth coverage.
- 14:00 Fourier Iteration Techniques in Antenna Measurement Applications Using Limited Data (Invited)
- We present results of our investigation on the use of Fourier iteration techniques to determine the antenna boresight far field from limited Fresnel region measurements in one or two planes. Measurements on two planes are well-suited to antennas not characterized by planes, such as those enclosed by radomes. Fourier iteration between two near field measurement planes also has the potential to remove multiple reflections when measuring aperture antennas.
- 14:20 On-body Antennas: Design Considerations and Challenges (Invited)
- This paper highlights the considerations and challenges when designing antennas suitable for on-body communication in Wireless Body Area Networks. Designing antennas that are required to operate in near body scenario make it more challenging for antenna designers as several important factors need to be taken into consideration along with the human body effects. These factors include antenna detuning, impedance matching, radiation pattern, Specific Absorption Rate, size, cost, weight, positioning, bending and stable performance with the variation of the gap between the antenna and the human body. An antenna addressing these challenges is suitable for on-body communication and wearable applications.
- 14:40 Demonstration of mmWave Systems and Networks for the HetNet in 5G Mobile Communication (Invited)
- Latest success of open experiments of mmWave systems and networks for the Heterogeneous network in 5G Mobile Communication are reviewed. This is conducted in "wireless-fiber project" funded by the Ministry of Internal Affairs and Communications, Japan and high-speed wireless communication systems above Gbps has been pursued by the collaborative team in Tokyo Institute of Technology as well as the industries for almost a decade.
- 15:00 Pulsed Helical Antenna for High-Power Applications
- Helical antenna is a very versatile antennas capable of producing many different types of radiation characteristics. Its performance is bounded by a loop (length going to 0) and a dipole (major diameter going to 0). Within these bounds, the helical antenna radiates a ~ circularly polarized electromagnetic wave with varying characteristics. In this paper we describe its applicability for high-power applications.
- 15:20 Dual-Frequency Reconfigurable Patch Antenna with Thermal Switches for Temperature Monitoring (invited)
- A dual-frequency reconfigurable sensing antenna is proposed for temperature monitoring. A double-patch antenna with two slots is designed for dual-frequency matching with a RFID chip at Ultra High Frequency (UHF) band. Thermal switches are added to the two slots to reconfigure the resonant frequencies according to the surrounding temperature. The proposed antenna exhibits a high sensitivity, a compact size, and the capability of self-reference.

Conveners: Rolf Schuhmann and Sebastian Schöps

Room: EChairs: Rolf Schuhmann, Sebastian Schöps

- 13:40 An Application of ParaExp to Electromagnetic Wave Problems (Invited)
- Recently, ParaExp was proposed for the time integration of hyperbolic problems. It splits the time interval of interest into sub-intervals and computes the solution on each sub-interval in parallel. The overall solution is decomposed into a particular solution defined on each sub-interval with zero initial conditions and a homogeneous solution propagated by the matrix exponential applied to the initial conditions. The efficiency of the method results from fast approximations of this matrix exponential using tools from linear algebra. This paper deals with the application of ParaExp to electromagnetic wave problems in time-domain. Numerical tests are carried out for an electric circuit and an electromagnetic wave problem discretized by the Finite Integration Technique.
- 14:00 Consideration on Implementation of Dispersive Materials into FDTD Dataflow Machine (Invited)
- To aim to ultra-high performance computation for microwave simulations, author has been working in development of a dedicated computer of Finite Difference Time Domain (FDTD) method with a dataflow architecture, the FDTD dataflow machine. This paper discusses microwave simulations for dispersive material by using the FDTD dataflow machine.
- 14:20 High-Quality Discretizations for Microwave Simulations
- We apply high-quality discretizations for simulating electromagnetic microwaves. Instead of the vector field presentations, we focus on differential forms, and discretize the model in spatial domain by the discrete exterior calculus. At the discrete level, both the Hodge operators and the time discretization are optimized for time-harmonic simulations.
- 14:40 A Locally Implicit FDTD Scheme with Relaxed Time Step Constraint for Non-Uniform Meshes
- We propose a method to use an extension of the wellknown FDTD algorithm on meshes that would typically imply severe time step size restrictions due to small geometrical details. For this purpose, the Newmark-Beta scheme, which is much less sensitive to mesh inhomogeneities with respect to numerical stability, is incorporated. Due to the reduced efficiency and accuracy of Newmark-Beta, we provide means of selectively applying it only to those parts of the mesh that would otherwise deteriorate FDTD's time step size.
- 15:00 Time-Domain Simulation of Electromagnetic Fields Based on Frequency-Domain Reduced-Order Models Including Debye Materials
- This contribution presents a new technique for constructing time-domain models from finite-element based simulation data in the frequency-domain, including frequency-dependent materials of Debye type. In order to reduce computational costs, projection-based model-order reduction techniques are applied. Not only do they provide an accurate input/output description of the system but also allow for reconstructing the electromagnetic fields. The resulting reduced-order model is proven to be passive, which is crucial for preserving causality in time-domain simulations.

Conveners: Matteo Pastorino and Lianlin Li

Room: BChairs: Matteo Pastorino, Lianlin Li

- 16:00 Alphabet CS for Inverse Scattering (Invited)
- An Alphabet Compressive Sensing (CS) approach is proposed in this paper for the retrieval of arbitrarily-shaped targets when no a-priori information on the class of scatterers at hand is available. The approach is based on the combination of (i) a fast CS retrieval methodology that is employed to invert the field data assuming several different candidate expansion bases (i.e., the alphabet), and (ii) a robust and effective algorithm for the (non-supervised) selection of the best reconstruction among those obtained with the available alphabet. Such a strategy allows to minimize the a-priori information necessary to obtain sparse representations of the unknown targets A preliminary numerical experiment is reported to validate the proposed methodology.
- 16:20 Solving the PEC Inverse Scattering Problem with A Linear Model
- In this paper, the nonlinear perfect electric conductor (PEC) inverse scattering problem was addressed with a linear model. First, finite difference frequency domain (FDFD) was used to discretize the problem. Then, the contrast and the total field were included into the contrast source to formulate a linear model. Due to the fact that the induced current only exists on the surface of the PEC scatterers, reconstruction methods in compressive sensing (CS) can be used to recover the contrast source which is able to indicate the shape of the PEC objects. To further enhance the inversion performance, multiple measurement vector (MMV) model was used to exploit the joint sparsity of the contrast sources corresponding to different incident angles. This method share some common merits with other inversion methods: First, it does not require a priori information on the position and quantity of the scatterers. Second, nonconvex PEC objects can be successfully reconstructed. Third, it enables simple incorporation with complicated background media without increasing extra computational burden. In addition, it also shows its own advantages that cannot be achieved in other inversion methods: First, it solves the nonlinear inverse scattering problems based on the vectorial Maxwell equations with a linear model in which no approximation has been used. Second, the sensing matrix is much less compared to the inverse of the stiffness matrix in FDFD scheme, so it can be computed and stored beforehand to circumvent the matrix inverse computation and achieve fast inversion. Numerical simulation results with transverse magnetic (TM) data in 2D configuration demonstrated the validity of the proposed method.
- 16:40 A Three-Dimensional Microwave Imaging Approach based on a Lp Banach Space Inversion Procedure (Invited)
- A three-dimensional microwave imaging inversion algorithm is proposed in this paper. The developed approach is based on an efficient inversion algorithm, performing a regularization in the framework of the Lp functional Banach spaces. In order to increase the computational efficiency of the method, two specific speed-up strategies have been developed. The performances of the method are preliminarily assessed by means of numerical simulations.
- 17:00 Direct Sampling Method for Monostatic Radar Imaging
- In this paper, we extend the use of conventional Direct sampling method (DSM) which is only applicable to the multistatic measurement data, to the monostatic measurement data for radar imaging applications. We define a novel testing function which can be used in the indicator function of DSM with monostatic data. Numerical examples demonstrate the feasibility of the proposed method.
- 17:20 Transmission of a Single Rectangular Hole Filled with Uniaxial Anisotropy Material (Invited)
- The transmission of a single rectangular hole filled with uniaxial anisotropy is investigated. After plane wave passes through the hole, there can be resonances at different frequencies with different value, which could also be affected by the ratio of long and short sides of the hole. Importantly, we discuss the influence of relatively conductivity tensor and relatively permeability tensor as to the resonant modes.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChairs: Mariana Nikolova Georgieva-Grosse, Piergiorgio L.E. Uslenghi

- 16:00 Electromagnetic Scattering by a Cylindrically-capped Metallic Wedge Perpendicularly Truncated by a Metal Plane (Invited)
- An arbitrarily directed and polarized plane electromagnetic wave is incident on a metallic structure consisting of a cylindrically-capped wedge perpendicularly truncated by an infinite plane. The total field is determined exactly, in the phasor domain. Particular attention is devoted to the surface currents on the structure.
- 16:20 Theorem for the T1(L,n) Numbers and its Application in the Electromagnetic Theory (Invited)
- The theorem for existence and for the main features of the T1(L,n) numbers (finite real positive numbers, near of kin to the positive zeros in the independent variable ro of the generalized in the Thompson and Barnett's sense real regular Coulomb wave function, is formulated by means of three lemmas and proved numerically. Lemma 1 reveals the existence of quantities and defines them for L - zero, a restricted positive or negative real number, different from a multiple of -1/2 , equal or less than -1 as the limit of the infinite sequence of real positive numbers. Lemma 2 treats the special case L=l/2-1. Lemma 3 discloses some of the properties of the numbers (relation for certain values of L, formula for symmetry, bond of some of them with the Ludolphian number and intervals of monotony). The influence of parameter L on T1(L,n) is shown in a tabular and graphical form, assuming n=1. An application of numbers in the theory of the circular waveguide, completely filled with azimuthally magnetized ferrite, under normal TE0n modes excitation, is presented.
- 16:40 An Introduction of the Generalized Wiener-Hopf Technique for Coupled Angular and Planar Regions (Invited)
- This paper presents the formulation of the electromagnetic problem constituted of coupled angular and planar regions by using the generalized Wiener-Hopf technique. The paper introduce also the technique to obtain a solution of the problem by reducing the factorization problem to Fredholm integral equation. The test case of a PEC planar waveguide filled by a dielectric medium that opens to a PEC angular region is presented.
- 17:00 Propagating Beam Frame: A Novel Formulation for Time-Dependent Radiation and Scattering (Invited)
- We present a novel strategy for tracking time-dependant waves. The theory is structured upon a discrete phase-space set of pulsed beam (PB) waves (space-time wavepackets), which is shown to constitute an overcomplete frame. We show that the field radiated by any time-dependent volume source distribution (with aperture sources being a special case) can be expanded as a sum of these PB wavefields. The expansion coefficients are obtained by projecting the source distribution over the dual frame set that has essentially the same structure as the basic set. This projection operation is recognized as a windowed Radon transform (WRT) in space-time, hence the frame is denoted as WRT propagating beam frame (WRT-PBF). The formulation generalizes the conventional Green's function and plane wave representations in the time domain. Applications to scattering and inverse scattering will be discussed.
- 17:20 Diffraction of a Creeping Wave by the Edge of a Strongly Elongated Spheroid Truncated by a Plane Perpendicular to its Axis (Invited)
- In this paper, the diffraction of a creeping wave by the edge of a truncated strongly elongated spheroid, is considered. Improved formulas for the diffracted field based on a new asymptotic solution of Maxwell's equations, for the creeping waves propagating along the generatrixes of the spheroid, are presented

Room: D

Chairs: Konstantin Bliokh, Filippo Capolino

- 16:00 Enhanced non-reciprocity induced by synergy of Dark-Modes and Faraday rotation
- Dark-mode of a small particle consists of two equally intense and mutually opposing dipolar excitations. Each of these two opposing dipoles may even resonate at or near the dark-mode frequency. Nevertheless, the net dipole moment of the system vanishes due to the destructive interference between the opposing dipoles, hence the dark-mode resonance cannot be observed externally. We show that under external magnetic bias the opposing dark-resonances of a plasmonic particle shift in opposite directions and create a region of extremely sensitive Faraday rotation. We show that the magnetized dark resonance in Ag particle may provide 50 degrees rotation under magnetic fields of the order of 1 Tesla.
- 16:20 Graphene-MoS2 Heterostructure Based Surface Plasmon Resonance Biosensor
- In this paper, a graphene-MoS2 heterostructure biosensor with silver (Ag) substrate based on the surface plasmon resonance (SPR) principle is presented. The biosensor is designed to sense at least one monolayer single stranded DNA (ssDNA) which has a thickness of 3.2 nm. The design process is performed according to the best minimum light intensity conception with Transfer Matrix Method (TMM). The background substrate formed by Ag film-MoS2-graphene is simulated numerically by increasing the number of graphene. During this process, the thickness of Ag-film is optimized by taking the light intensity into consideration. The results show that the sensitivity of the biosensor can be enhanced with the number of the graphene layers. The shift in resonance angle, i.e sensitivity, improves at the ratio of 13% with 5-layer graphene.
- 16:40 Low-Temperature Perspective of Microgap Thermophotovoltaics
- It is commonly thought that the thermophotovoltaic (TPV) electric generators operate only at very high temperatures. This condition implies that their heat sources must be gas burners, furnaces hot flue gases, combustors of the waste, etc. However, we theoretically show that a TPV system with sufficiently narrow cavity between the cold (photovoltaic) and hot (emitting) parts allows a high electric output (inherent to TPV systems) to arise from modest temperatures of the emitter (like those in thermoelectric power generators). This way one will be able to combine the advantages of the TPV system with those of the thermoelectric one. For it one has to introduce a wire metamaterial into a micron cavity. Nanowires are prepared in the cold layer and have free standing ends in the vacuum cavity without a contact to the hot surface.
- 17:00 Quantum Superradiant and Subradiant Modes in Plasmonic Nanochannels
- We present a new numerical modeling method to study superradiant and subradiant modes excited by a pair of quantum emitters embedded inside plasmonic nanochannels. These channels can provide an effective epsilon-near-zero (ENZ) response in their cut-off frequency and Fabry-Perot (FP) resonances in higher frequencies. The plasmonic resonant modes are found to enhance the constructive (superradiance) or destructive (subradiance) interference between two different quantum emitters located inside the channels. The separation distance between neighboring emitters and their emission wavelength can be changed to dynamically control the collective emission properties of the plasmonic system. It is envisioned that the dynamic modification between superradiant and subradiant modes will find applications to future quantum communication and computing systems.
- 17:20 Mantle Cloaks for Elliptical Cylinders Excited by an Electric Line Source
- We investigate the ability of surface impedance mantle cloaks for cloaking of elliptical cylinders excited by an electric line source. The exact analytical solution of the problem utilizing Mathieu functions is obtained and is used to derive optimal surface impedances to cloak a number of configurations. Specifically, theoretical designs are presented which can minimize the scattering from line source excited dielectric elliptical cylinders, as well as conducting strips immersed in such structures. It will be shown that the required surface impedances are angle-dependent; that their performance has limitations with respect to the source and observation point locations.

Conveners: Özgur Ergul and Pasi Ylä-Oijala

Room: EChairs: Ozgur Ergul, Pasi Ylä-Oijala

- 16:00 Fast computational techniques for modeling RFX-mod fusion devices on hybrid CPU-GPU architectures (Invited)
- We presents fast computational techniques applied to modelling the RFX-mod fusion device. We derive an integral equation model for estimating the current distribution in the conducting structures, and we compute the input-output transfer functions. By using hybrid CPU-GPU parallelization, speed-up factors of about 200 can be obtained against uniprocessor computation.
- 16:20 A Novel Beam-Steering Nonlinear Nanoantenna with Surface Plasmon Resonance (Invited)
- Plasmonic nanostructures that support surface plasmon (SP) resonance potentially provide a route for the development of engineered nonlinear optical media. In this work, a novel plasmonic particle-in-cavity nanoantenna (PIC-NA) is proposed. The second harmonic generation (SHG) of the PIC-NA under strong localized SP resonance is systematically analyzed by a self-consistent numerical solution based on boundary element method (BEM). The developed method solves the fundamental field and second harmonic (SH) field together iteratively to capture their mutual coupling. Strong enhancement of SHG from PIC-NA is achieved. The SHG enhancement factor is around four orders of magnitude, which is much higher than those achieved in literatures. Moreover, unidirectional SH radiation for the asymmetric PIC-NA is realized. Its emission direction can be controlled by the location of the nanosphere. The proposed novel plasmonic PIC-NA functions as the new synthetic second-order nonlinear optical material that has promising applications in the nonlinear sensing, spectroscopy and frequency generation.
- 16:40 Present and Future Challenges in Preconditioning Integral Equations for Electromagnetics (Invited)
- This talk will review present challenges in preconditioning electromagnetic integral equations and will delineate perspectives for the future of this domain. Special attention will be devoted to analyze conditioning problems and challenges in all regimes of interest for applications including the low-frequency, the high frequency, and the elliptic regime. Theoretical considerations will be matched by numerical examples that will corroborate the theory and show the practical impact of advanced preconditioning techniques on real case scenarios.
- 17:00 On Error Controlled Computing of the Near Electromagnetic Fields in the Shade Regions of Electrically Large 3D Objects (Invited)
- Current challenges in evaluation of the near electromagnetic fields in the shadow regions of electrically large objects are discussed. It is shown that traditional low order discretization techniques commonly used for analysis of radiation and scattering problems in the presence of electrically large platforms such as Fast Multipole Method accelerated Rao-Wilton-Glisson Method of Moments are incapable of computing such fields accurately. A roadmap to the solution of this open problem using higher-order boundary element schemes is discussed as well as difficulties associated with them. The Locally Corrected Nystrom method is used for demonstration of higher-order modeling capabilities.
- 17:20 Benchmarking to Close the Credibility Gap: A Computational BioEM Benchmark Suite
- The dearth of verification, validation, and performance benchmarks is identified as a roadblock to further progress in computational electromagnetics. The necessary ingredients for a useful benchmark suite are an application-specific list of problems, reference solutions, performance (error and computational cost) measures, and online databases publicizing comparisons. Computational cost comparisons are particularly difficult, rare, and important. As a case study, a benchmark suite for comparing existing and future computational bioelectromagnetics methods is developed.

Conveners: Daniel Sjöberg and Ben Zion Steinberg

Room: BChairs: Daniel Sjöberg, Ben Zion Steinberg

- 08:40 Controlling Pulsed EM Scattering of Receiving Antennas: The One-Port Case (Invited)
- A time-domain compensation theorem concerning EM scattering of a one-port antenna system is derived with the aid of the reciprocity theorem of the time-convolution type. The theorem describes the impact of a change in the antenna load on receiving-antenna scattering properties. Applications of the theorem are found in controlling the pulsed echo of a receiving antenna as well as in related theoretical aspects of receiving-antenna scattering theory.
- 09:00 Magnetoelectric Coupling without Electric and Magnetic Response? (Invited)
- We theoretically consider electrically small reciprocal particles, which show bianisotropic magneto-electric coupling. We study how strong the magneto-electric effect can be in comparison with the electric and magnetic polarizations induced directly by the corresponding electric and magnetic incident fields. In particular, we prove that it is not possible to realize a passive reciprocal particle, which would have exactly zero electric or magnetic polarizability but still exhibit magneto-electric coupling effects. On the other hand, we prove that magneto-electric coupling coefficient can be very large as compared to both electric and magnetic polarizabilities of the same particle, in contrast to some claims found in the literature.
- 09:20 A multi-resolution 4-D FFT approach to parametric boundary integral equations for helical structures (Invited)
- This paper gives a report of an ongoing research to develop parametric boundary integral equations for helical structures and their application in the computation of induced currents and losses in three-phase power cables. The proposed technique is formulated in terms of the Electric Field Integral Equation (EFIE) or the Magnetic Field Integral Equation (MFIE) for a penetrable object together with the appropriate periodic Green's functions and a suitable parameterization of the helical structure. A simple and efficient numerical scheme is proposed for the computation of the impedance matrix in the Method of Moments (MoM) which is based on a multi-resolution 4-D FFT computation followed by polynomial extrapolation. Numerical examples are included demonstrating that the singular integrals have almost linear convergence and hence that linear or quadratic extrapolation can be used to yield accurate results.
- 09:40 Nonnegative Energy for Dipolar Continua (Invited)
- Positive semi-definite (nonnegative) expressions for the time-domain macroscopic energy density in passive, spatially nondispersive dipolar continua are derived from the underlying microscopic Maxwellian equations satisfied by classical models of discrete bound dipolar molecules or inclusions of the material or metamaterial continua. The microscopic derivation reveals two distinct positive semi-definite macroscopic energy expressions, one that applies to diamagnetic continua (induced magnetic dipole moments) and another that applies to paramagnetic continua (alignment of permanent magnetic dipole moments). The difference between the macroscopic paramagnetic and diamagnetic energy expressions is equal to a "hidden energy" often attributed to Amperian magnetic dipoles. The microscopic derivation reveals that this hidden energy is drawn from the reservoir of inductive energy in the permanent microscopic Amperian magnetic dipole moments.
- 10:00 State-space models for stored energy and Q-factors (Invited)
- Q-factors are often used to quantify bandwidth performance of resonant structures. The Q-factor is defined as the quotient between the stored and the dissipated energies. The dissipated energy can be reformulated as the dissipated power and is in general well defined. The definition and evaluation of the stored energy is much more challenging and there are presently several proposals but none is applicable for general radiating system. The main challenge is to separate the radiated and stored parts of the total energy. In this paper, an alternative approach is proposed that is based on a state-space model of the antenna. The state-space model describes the internal states of the system and models the states that store the energy. The state-space model is determined of the impedance matrix from the electric field integral equation. This provides a computationally efficient way to determine the stored energy that can be used in antenna current optimization. The state-space approach also offers new insight into the challenges to define the stored energy for electrically large objects.
- 10:20 Invariant Dispersion Relation for Anisotropic Media
- We study electromagnetic wave propagation in anisotropic dielectric media with two generic matrices of permittivity and permeability. We present a compact expression of the dispersion relation for this media. It is invariant under arbitrary curvlinear transformations of the coordinates. Some consequences of this relation are derived.

Convener: Paul Smith

Room: CChairs: Christophe Craeye, Paul Smith

- 08:40 Physical bounds and automatic design of antennas above ground planes
- Physical bounds for antennas above ground planes are calculated by optimizing the antenna current. The bounds are compared with antennas modeled as fragmented patches and optimized using genetic algorithms. Monopole structures over ground planes are modeled with image theory and optimized. The monopole over ground plane structure simplifies experimental verification of the bounds.
- 09:00 The Effect of Rounding Vertices on the Diffraction from Polygons and Other Scatterers (Invited)
- The changes induced in the near- and far-field scattering by rounding the corners of an illuminated obstacle are discussed as a function of the radius of curvature near such corners. Dirichlet, Neumann or impedance boundary conditions are imposed on the surface. An integral equation formulation is employed; it is found that a graded mesh is necessary to obtain accurate results as well as to enable efficient calculation.
- 09:20 A series representation for the intermediate-field transmittance between apertures
- A recent communication provided a model for the transmittance between two antennas supporting Orbital Angular Momentum modes. That formulation involved a single integral along the radial spectral coordinate. That approach actually also applies to any pair of apertures supporting arbitrary distributions. Asymptotically, for far field conditions, an analytical expression has been developed, as a power of the near-field parameter, corresponding to the ratio between the far-field limit and the distance between antennas. This expansion is extended to the intermediate-field region, as a polynomial of the near-field parameter. The convergence of this method is discussed, along with the corresponding time savings and limitations.
- 09:40 Convergence of Fictitious Sources Methods Applied to Three-Dimensional Scattering Problems
- Computational methods, utilizing representations of the approximate solution of a boundary value problem as a finite superposition of fields of fictitious sources located outside the problem's domain, are widely used in the numerical modeling of wave scattering and radiation problems. In this work, we investigate certain convergence issues related to the field solutions derived by the application of fictitious sources methods to three-dimensional (3-D) scattering problems. The main result concerns the divergence and oscillations of the source strengths and the simultaneous convergence of the field generated by these divergent strengths. The origin of the oscillations is discussed and it is shown that they are not due to round-off errors or matrix ill-conditioning.
- 10:00 Numerical study of multilayered nonlinear inhomogeneous waveguides in the case of TM polarization (Invited)
- We consider propagation of surface TM waves in a circular dielectric waveguide filled with nonlinear (Kerr nonlinearity) multilayered inhomogeneous medium. Each layer is characterized by a specific value of the nonlinearity coefficient α. Analysis is reduced to solving a nonlinear transmission eigenvalue problem for an ordinary differential equation; eigenvalues of the problem correspond to propagation constants of the waveguide. For the numerical solution, a method is proposed based on solving an auxiliary Cauchy problem (a version of the shooting method). As a result of comprehensive numerical modeling, new propagation regimes are discovered.
- 10:20 Dynamics of Interstellar Dust Particles in Electromagnetic Radiation Fields
- We establish the theoretical framework for solving the equations of motion for an arbitrarily shaped, isotropic, and homogeneous dust particle in the presence of radiation pressure. The scattering problem involved is solved by a surface integral equation method, and a rudimentary sketch of a numerical implementation is introduced with preliminary results agreeing with predictions.

Conveners: Valentin Freilikher and Ehud Heyman

Room: DChairs: Valentin Freilikher, Ehud Heyman

- 08:40 Disorder-induced Light Localisation: from Random to Artificial (Invited)
- Light localisation in one-dimensional (1D) randomly disordered medium is usually characterized by randomly distributed resonances with fluctuating transmission values, instead of selectively distributed resonances with close-to-unity transmission values that are needed in real application fields. By a resonance tuning scheme developed recently, opening of favorable resonances or closing of unfavorable resonances are achieved by disorder micro-modification, both on the layered medium and the fibre Bragg grating (FBG) array. And furthermore, it is shown that those disorder-induced resonances are independently tunable. Therefore, selected resonances and arranged light localisation can be achieved via artificial disorder, and thus meet the demand of various application fields.
- 09:00 Disorder-induced mutation of quasi-normal modes in 1D open systems (Invited)
- We study the relation between quasi-normal modes (QNMs) and transmission resonances (TRs) in one-dimensional (1D) disordered systems. We show that while each maximum in the transmission coefficient is always related to a QNM, the reverse statement is not necessarily correct. There exists an intermediate state, where only part of the QNMs are localized and provide a resonant transmission. The rest of QNMs (strange modes) are not localized and not associated with any anomalies in the transmission. The ratio of the number of the normal QNMs to the total number of QNMs is independent of the type of disorder, and varies slightly in rather wide ranges of the strength of a single scattering and the length of the random sample.
- 09:20 In situ search for 3D Anderson localization of ultrasound in resonant emulsions (Invited)
- "After more than a half century of Anderson localization, the subject is more alive than ever" [1]. In acoustics, the first observation of sound localization in three dimensions has been reported in a random elastic network of aluminum beads, a so-called "mesoglass" [2]. Here, we propose to investigate this complex wave phenomenon by studying ultrasonic wave transport through in situ experiments performed within an all-fluid system of disordered resonant scatterers, so-called "resonant emulsions".
- 09:40 Particle-like wave packets in complex scattering systems (Invited)
- A wave packet undergoes a strong spatial and temporal dispersion while propagating through a complex medium. This wave scattering is often seen as a nightmare in wave physics whether it be for focusing, imaging or communication purposes. Controlling wave propagation through complex systems is thus of fundamental interest in many areas, ranging from optics or acoustics to medical imaging or telecommunications. Here, we study the propagation of elastic waves in a disordered waveguide by means of laser interferometry. We demonstrate how the direct experimental access to the information stored in the scattering matrix of these systems allows us to selectively excite scattering states and wave packets that travel along individual classical trajectories. Due to their limited dispersion, these particle-like scattering states will be crucially relevant for all applications involving selective wave focusing and efficient information transfer through complex media.
- 10:00 Invariant Imbedding Theory of Wave Propagation in Stratified Anisotropic Media (Invited)
- We study wave propagation characteristics in stratified anisotropic media theoretically using the invariant imbedding method. We consider the cases where some component of the permittivity tensor is a periodic or random function of a space variable and investigate the photonic band gap structure and the Anderson localization phenomenon. We also consider the case where the tensor component in the longitudinal direction varies from positive to negative values and the associated mode conversion and resonant absorption phenomena.
- 10:20 Spatio-temporal imaging of light transport in strongly scattering media (Invited)
- We report on the passive measurement of time-dependent Green's functions in the optical frequency domain with low-coherence interferometry. Inspired by previous studies in acoustics and seismology, we show how the mutual coherence function of a broadband and incoherent wave-field can directly yield the Green's functions between scatterers of a complex medium. Both the ballistic and multiple scattering components of the Green's function are retrieved. This simple and powerful approach directly yields a wealth of information about the medium under investigation. In particular, it allows to investigate locally the growth of the diffusive halo within the scattering medium. Local measurements of transport parameters can thus be performed and allow to image a strongly scattering layer with a unprecedented resolution of a few transport mean free paths. This constitutes a major breakthrough compared to state-of-the-art techniques such as optical diffuse tomography.

Conveners: Thomas Eibert and Francesco Andriulli

Room: EChairs: Thomas F. Eibert, Francesco Andriulli

- 08:40 Trigonometric Polynomial Expansion and Multilevel Fast Multipole Algorithm
- Radiation patterns can be spanned with trigonometric polynomials in Multilevel Fast Multipole Algorithm (MLFMA) allowing development of simple global interpolators with exceptional accuracy control. In this article the basic properties of these functions are studied in one variable case. It is shown how orthogonality of the basis functions can be utilized to develop simple operations suitable for creating fast and accurate MLFMA implementations.
- 09:00 Fast Inverse Equivalent Current Solutions with Surface Currents in Complex Space
- Inverse equivalent current solutions for single frequency field transformations of measured or computed field observations work commonly with electric and/or magnetic surface current densities. Often the field observation equations are augmented by a null-field condition in form of an integral equation for the region external to the Huygens surface. As an approximate and inexpensive alternative to the null-field condition, we propose to work with directive current sources, which are obtained by shifting the equivalent surface current densities into complex space. These sources are integrated into the fast irregular antenna field transformation algorithm which achieves low numerical solution complexity by utilizing multilevel fast multipole like principles. Field transformation results based on realistic measurement data are presented to demonstrate the functionality of the surface current densities in complex space.
- 09:20 Broadband Multilevel Fast Multipole Algorithm For Large-Scale Problems With Nonuniform Discretizations (Invited)
- We present a broadband implementation of the multilevel fast multipole algorithm (MLFMA) for fast and accurate solutions of multiscale problems involving highly nonuniform discretizations. Incomplete tree structures, which are based on population-based clustering with flexible leaf-level boxes at different levels, are used to handle extremely varying triangulation sizes on the same structures. Superior efficiency and accuracy of the developed implementation, in comparison to the standard and broadband MLFMA solvers employing conventional tree structures, are demonstrated on practical problems.
- 09:40 Fast Computation of Modified Green's Function for Generalized Source Integral Equation Solvers (Invited)
- A technique for the fast computation of modified Green's function arising from the generalized source integral equation (GSIE) formulation is proposed. The method is based on an efficient sampling and tabulation of the modified Green's function, which comprises two components: a direct free-space component and an additional contribution by electric and magnetic sources designed to "shield" the source from certain observation regions. The efficient sampling of the sum of both contributions is performed by using nonuniform grids designed in accordance with the wave-field phenomenology unique to the source-"shield" configuration. The proposed method's performance is demonstrated for representative examples.
- 10:00 Theory of Characteristic Modes based on Potential-Based Integral Equation (Invited)
- The characteristic mode analysis is presented based on the potential-based integral equation, where the vector potential equation and the scalar potential are formulated separately and solved in tandem. Accordingly, the theory of the characteristic modes, originated from the electrical field integral equation (EFIE), can be analyzed for the novel potential-based integral equation system with the contributions from different components in EFIE.
- 10:20 MLFMA, PO and Hybrid MLFMA-PO for Impedance Boundary Condition (Invited paper)
- Multilevel fast multipole algorithm (MLFMA), physical optics (PO), and their combination, hybrid MLFMA-PO, are developed for the radar cross section computation of electrically large imperfectly conducting objects modelled with the impedance boundary condition. Surface integral equation formulation of the problem is based on the self-dual integral equation formulation by Yan and Jin. Numerical properties of the methods are investigated for various surface impedances.

Chair: Kazuya Kobayashi

- A Well-Conditioned, Hermitian, Positive Definite, Combined Field Integral Equation for Simply and Multiply Connected Geometries (Invited)
- We present a new preconditioner for the combined field integral equation (CFIE) that gives rise to a Hermitian, positive definite system of linear equations. Differently from other Calderon strategies, this scheme necessitates a standard discretization of the electric field integral equation (EFIE) with Rao-Wilton-Glisson (RWG) basis functions (i.e., no dual EFIE matrix required), is free from spurious resonances, and is stable down to the static limit for both simply and multiply connected geometries. The fact that the new system matrix is Hermitian, positive definite, and well-conditioned makes it amenable for fast iterative and direct solvers. Numerical results demonstrate the effectiveness of the proposed approach
- Semiclassical Modeling of Individual and Arrayed Nanoantennas in the Quantum Plasmonic Regime
- We put forward here design and semiclassical modeling of nonlinear and reconfigurable optical metasurfaces formed by arrayed nanoantennas with nano/subnano-scale feed-gaps, where the photon-assisted tunneling results in a set of linear/nonlinear quantum conductivities. We show that optical nonlinearities sourced from higher-order quantum conductivities may be boosted by the plasmonic resonance and the large local field enhancement in the load region of nanoantenna. We discuss two exciting applications of the proposed nanoantenna-based devices: efficient frequency multiplication at the nanoscale and dynamic resistive switching for holographic imaging.
- Boundary shape reconstructions in a coaxial waveguide using Bessel functions
- This paper investigates boundary shape reconstructions in coaxial waveguides using microwave scattering. Electromagnetic field perturbation theory together with inverse problem theory is used to reconstruct two-dimensional small boundary deformations on the inner boundary of a coaxial waveguide. Due to the first-order perturbation theory employed, the scattering parameters of the waveguide have linear dependencies on the continuous deformation function. Thus, the corresponding inverse problem can be linearized, and direct inversion can be employed to obtain the shape parameters. Tikhonov regularization is used to regularize the resulting ill-conditioned linear system. Finally, reconstruction results are presented for a few examples of two-dimensional localized shape deformations of coaxial waveguide boundaries, being in agreement with the known actual shapes.
- Electromagnetic wave propagation in metamaterials: a visual guide to Fresnel-Kummer surfaces and their singular points
- The propagation of light through bianisotropic materials is studied in the geometrical optics approximation. For that purpose, we use the quartic general dispersion equation specified by the Tamm-Rubilar tensor, which is cubic in the electromagnetic response tensor of the medium. A collection of different and remarkable Fresnel (wave) surfaces is gathered, and unified via the projective geometry of Kummer surfaces.
- Improved Result for the Refractive Index of Human Hemoglobin Solutions by Kramers-Kronig Relations
- Applying Kramers-Kronig relations we compute the real part of the refractive index of aqueous solutions of human hemoglobin from its absorption spectra in the range 250 nm-1100 nm. Since the solution's absorption is not limited to this spectral range, strong ultraviolet (UV) and infrared absorbance of the water have been considered in previous investigations [Sydoruk et al., J. Biomed. Opt. 17(11), 2012]. We improve these results regarding the concentration-dependent absorption of water, the UV absorbance of hemoglobin's peptide-backbone, and by fixing the remaining unknown parameters via a global fit.
- Transfer operator approach for cavities with apertures
- We describe a representation of the boundary integral equations for wave propagation in enclosures which leads to a direct description of transport and dynamical characteristics of the problem. The formalism is extended to account for arbitrary and possibly statistical sources driving a polygonal cavity problem and to account for apertures. In this approach, the boundary integral equations are encoded within a shift operator which propagates waves leaving the boundary until they return to the boundary as an incoming wave. The response of the system to non-deterministic, statistical sources characterized by correlation functions can be treated, providing a direct path to ray-tracing approaches through the Wigner function. The high frequency limit is retrieved semi-classically and provides a simple ray tracing scheme transporting densities of rays as an averaged response. Interference effects due to transport along multiple paths can also be accounted for.
- Scattering Analysis of Asymmetric Metamaterial Resonators by the Riemann-Hilbert Approach
- This work presents an analytical treatment of an asymmetric metamaterial-based resonator excited by an electric line source, and explores its beam shaping capabilities. The resonator consists of two concentric cylindrical material layers covered with an infinitely thin conducting shell with an aperture. Exact analytical solution of the problem is derived; it is based on the n‒series approach which is casted into the equivalent Riemann-Hilbert problem. The examined configuration leads to large enhancements of the radiated field and to steerable Huygens-like directivity patterns. Particularly, the directivities can be reshaped by changing the source location, as well as the extent of the aperture. The present results may provide alternative strategies for beam shaping and may contribute to development of novel nano-antenna designs.
- Effective Parameter Calculation of 3D Bianisotropic Scatterer Arrays through Extracted Polarizabilities
- In this paper, an efficient technique for computing the bulk parameters of infinite, normally-illuminated 3D arrays is developed. Initially, the dispersion equation of the array is derived and, then, the complex wavenumber for the TEM case is obtained through a rigorous algorithm. The retrieved polarizabilities of a single scatterer and the wavenumber are, finally, incorporated in first-principles homogenization formulas to evaluate the effective parameters. The proposed method is applied to popular bianisotropic scatterers and the validity of the results is successfully certified via numerical simulations.
- Numerical Investigation of DB Metamaterial and Retrieval of its Effective Parameters
- DB boundary conditions require vanishing of normal components of electric and magnetic flux density vectors on the boundary surface. In this paper, we present a free-space simulation analysis of the unit-cell structure proposed for the realization of a metamaterial exhibiting DB boundary conditions. From numerically calculated reflection and transmission parameters all components of the effective permittivity and permeability tensors, characterizing the DB material, are retrieved both in the axial as well as in the orthogonal directions to the metamaterial boundary. Such effective constitutive parameters are extracted using S-parameter inversion technique for obliquely incident wave.
- Structuring Band-pass Dispersion with Cascaded High- and Low-pass Optical Metatronic Metasurfaces
- In the paradigm of optical metatronics, metasurfaces with multi-layered structures can be engineered to behave as multi-ordered filters for desired spectral dispersions, such as low-pass, high-pass, band-pass, and band-stop cases, following and inspired by electronic circuit design procedures. However, there is a constraint in the design of layered band-pass metatronic filters with narrow bandwidth. Based on the concept of metatronic metasurfaces, a new method is proposed to achieve optical band-pass dispersion by cascading a pair of metatronic high-pass and low-pass metasurface filters. The proposed method is also numerically validated in the higher-ordered band-pass filter design with sharper transition slopes to the stopband. The results of our numerical simulations illustrate the possibility for such multi-ordered optical band-pass filters with narrow bandwidth, augmenting the procedures for dispersion engineering using layered metatronic metasurfaces.
- Selected features of metamaterials with near-zero parameters
- Metamaterials with near-zero parameters exhibit unique features that enable the exploration of qualitatively different physics in classical and quantum electrodynamics. In our presentation, we will present a review of some of the most relevant phenomena and our ongoing efforts in this area. In particular, we will emphasize the geometry-invariant properties that arise from the decoupling of spatial and temporal field variations, leading, for example, to the excitation of bound states whose eigenfrequency is independent of the geometry of the external boundary. We also specifically address the reversible decay dynamics experienced by a two-level system coupled to these bound eigenmodes, even under the deformation of the external boundary of the cavity.
- Volume Potential-Integral-Equation Formulation for Electromagnetic Scattering by Dielectric Objects (Invited)
- A volume potential-integral-equation formulation for electromagnetic scattering by dielectric objects is developed and discretized with fully continuous nodal basis functions. The equations are tested with either the point-matching or Galerkin's testing procedure. Galerkin's testing shows superior accuracy over the point-matching as well as over the standard discretization of the electric field volume integral equation with Schaubert-Wilton-Glisson (SWG) functions. The potential formulation is accelerated by the precorrected-FFT method.
- An Application of ParaExp to Electromagnetic Wave Problems (Invited)
- Recently, ParaExp was proposed for the time integration of hyperbolic problems. It splits the time interval of interest into sub-intervals and computes the solution on each sub-interval in parallel. The overall solution is decomposed into a particular solution defined on each sub-interval with zero initial conditions and a homogeneous solution propagated by the matrix exponential applied to the initial conditions. The efficiency of the method results from fast approximations of this matrix exponential using tools from linear algebra. This paper deals with the application of ParaExp to electromagnetic wave problems in time-domain. Numerical tests are carried out for an electric circuit and an electromagnetic wave problem discretized by the Finite Integration Technique.
- Near-field Coupling in UHF-RFID Printer-Encoders
- In the framework of Near-field (NF) UHF-RFID applications, printer-encoder antennas represent an interesting scenario to investigate. In commercial RFID printer-encoders, the distance between the encoder and transponder antennas is typically a few millimeters only, and the encoder antenna has to reliably communicate with only one targeted tag among a number of tightly spaced transponders in very close proximity. In this paper, a number of encoder antenna layouts have been numerically analyzed in terms of power delivered to the transponder chip, by considering two commercial RFID tags. Moreover, the spatial selectivity of the encoder antennas is estimated. As a result, a reader antenna identical to the tag antenna is suggested as an optimal solution for meeting the severe requirement on the spatial selectivity of the encoding process.
- Sub-Voxel Refinement Method for Tissue Boundary Conductivities in Volume Conductor Models
- The resolution and element type of the mesh used in finite element method modelling of tDCS affect greatly on both the accuracy of the solution and computation time. Usually tetrahedral meshing is used in these models as they approximate curvature well but they are slow to solve. Using a voxel grid as the mesh reduces the computation time significantly but the cubical elements are not the most suitable option for curved surfaces. Tissue boundaries can be modelled as a layer of voxels with an average conductivity of the surrounding tissues. However, as the boundary being modelled only rarely divides a voxel into two equally sized portions, this approach is often erroneous. In particular with low resolutions. In this paper we propose a novel method for improving the accuracy of anatomically correct finite element method simulations by enhancing the tissue boundaries in voxel models. In our method, a voxel model is created from a set of polygonal surfaces segmented from MRI data by first voxelizing with a fine resolution and then increasing the voxel size to wanted resolution and calculating the ratio of fine voxels in- and outside the surface within each coarse voxel. Thus a more accurate proportions for the volume of a coarse voxel inside and outside the tissue boundary is achieved and its conductivity can be better approximated. To test the performance of this method, a series of simulations of motor cortical tDCS were performed using resolutions from 0.2 mm to 2 mm scaled to 0, 2 or 4 times finer resolution. Based on the results, the voxel size can be doubled with a cost of 3% in relative error by using our method and thus the modelled DOFs can be decreased by 87% and the simulation times decreased by 82%.
- A Floquet Wave Theory for Curvilinear Locally Periodic Boundary Conditions (Invited)
- In this paper, we discuss an extension of the Floquet-wave theory to curvilinear locally periodic boundary conditions. The local periodicity of curvilinear impedance surfaces is exploited to adiabatically apply the Floquet Wave theorem to fields and currents. We show that this extension allows for a good description of the interaction between the currents and the curvilinear boundary conditions. Based on this, it is possible to set an efficient design procedure for modulated metasurface antennas. Numerical results are provided to demonstrate the validity of the proposed approach
- Enhancing the Design of Textile Antennas with a Polynomial Chaos-based Stochastic Framework (Invited)
- A stochastic framework is presented to enhance the design of textile antennas, by addressing the impact of production uncertainties, substrate bending and compression on the performance of textile antennas. Each effect is considered separately and the probability density functions corresponding to the design parameters undergoing variations are experimentally estimated. In order to accurately quantify the statistical distribution of the antenna's figures of merit corresponding to these variations, we introduce a stochastic collocation method based on a generalized polynomial chaos technique or on Pade' approximants.
- Nonlinear Guided Electromagnetic Waves in a Layer: Revisiting an Old Problem and New Results (Invited)
- It is shown that for transverse-electric (TE) waves an open plane waveguide filled with a nonlinear medium of Kerr type supports two different physically interesting guided regimes in the focusing case. One of them has been studied in [Phys. Rev. A 91, 013840 (2015)], for the other one we could not find any record in the literature; in each of the regimes there exists an infinite number of guided waves. In the latter case the corresponding linear problem has no solutions (this case can be applied for negative permittivities). It is also shown that in the defocusing case only one regime arises with a finite number of guided waves; in this case all the solutions have linear counterparts (an infinite number of guided waves exist only in the focusing cases). In addition, it is demonstrated that open and shielded plane waveguides filled with Kerr medium have qualitatively different properties due to the nonlinearity.
- A Novel Beam-Steering Nonlinear Nanoantenna with Surface Plasmon Resonance (Invited)
- Plasmonic nanostructures that support surface plasmon (SP) resonance potentially provide a route for the development of engineered nonlinear optical media. In this work, a novel plasmonic particle-in-cavity nanoantenna (PIC-NA) is proposed. The second harmonic generation (SHG) of the PIC-NA under strong localized SP resonance is systematically analyzed by a self-consistent numerical solution based on boundary element method (BEM). The developed method solves the fundamental field and second harmonic (SH) field together iteratively to capture their mutual coupling. Strong enhancement of SHG from PIC-NA is achieved. The SHG enhancement factor is around four orders of magnitude, which is much higher than those achieved in literatures. Moreover, unidirectional SH radiation for the asymmetric PIC-NA is realized. Its emission direction can be controlled by the location of the nanosphere. The proposed novel plasmonic PIC-NA functions as the new synthetic second-order nonlinear optical material that has promising applications in the nonlinear sensing, spectroscopy and frequency generation.

Stored
Energy and Antenna Current Optimization

Mats Gustafsson

Room: BChair: Kazuya Kobayashi

- 13:40 Stored Energy and Antenna Current Optimization (Plenary)
- Antenna current optimization is used to determine optimal current distributions in the design region. The currents provide understanding, physical bounds, and figures of merits for antenna designs. The antenna current optimization problem is formulated as a convex optimization problem. The Q-factor is defined as the quotient between the stored and dissipated energies and is used to quantify the bandwidth performance of resonant structures. An approach based on a state-space model of the antenna input impedance proposed. The state-space model describes the internal states of the system and models the states that store the energy. The state-space model is determined from the impedance matrix of the electric field integral equation. In this presentation, antenna current optimization and stored electromagnetic energy expressions are reviewed. Numerical results for maximization of the gain to Q-factor quotient and minimization of the Q-factor for prescribed radiated fields are presented.

Convener: Ari Sihvola

Room: BChair: Ari Sihvola

- 14:40 Maxwell's Approach to Deriving the EM Field Equations in Dipolar Continua (Invited)
- Maxwell obtained his electromagnetic field equations in dipolar continua without using macroscopic averaging by defining mathematically the fields within source regions by the same potential integrals that he used to define these fields in free space outside of source regions. Maxwell illustrated this method explicitly in his derivation of the magnetostatic equations within magnets (magnetization) where he related the mathematically defined fields to fields one can measure, in principle, in free-space cavities within the magnetization. Here in this paper, we apply the same approach to obtain the general time-dependent Maxwell equations in dipolar continua and confirm by a straightforward derivation that these equations are also obtained from macroscopic averaging of the sources and fields of discrete electric and magnetic dipoles.
- 15:00 Oliver Heaviside, Eccentric Electrician and Master of Maxwell's Theory (Invited)
- Oliver Heaviside devoted his whole life to polishing Maxwell's theory to a workable instrument. His life and achievements are reviewed in this paper.
- 15:20 On the Metamorphoses of Maxwell's Equations During the Last 150 Years ― spotlights on the history of classical electrodynamics ― (invited)
- We outline Maxwell's five decisive papers on his equations governing electrodynamics (1862-1868). We study the metamorphoses of these equations and find essentially twelve different versions of them. We express our preference for the so-called premetric version of the Maxwell equations, which is particularly useful in understanding the structure of electrodynamics. Some selected applications are discussed.

Convener: Paul Smith

Room: CChairs: Christophe Craeye, Paul Smith

- 14:40 Study of Field Misalignment in a Cavity Used for Atomic Clock Applications
- In vapor cell atomic clocks the atom-field interaction is typically obtained inside a microwave cavity resonator in which the microwave driving field together with a static magnetic field and an optical field are applied to excite the atoms. These fields are generally well-controlled, mutually aligned to a common quantization axis. Since the exploited atomic transition is sensitive to any potential axis misalignment, the performance of the clock can also be affected. We study the effect of such misalignment for the case of a cylindrical cavity used in vapor-cell atomic clocks, taking into account the misalignments of the optical detection field and the static magnetic field required for the atomic transition. Both the geometry of the cavity and the factors contributing to losses can play role in the degradation of the signal and need to be taken into account in the misalignment problem discussed.
- 15:00 Error model for Contour-FFT evaluation of the free-space on-plane Green's function
- Closed-form analytical expressions are derived for the numerical integration of spectral Green's function with Contour-FFT. Results indicates that a proper uniform grid of spatial points enhances the convergence rate of the truncation error, that the Nyquist-Shannon sampling theorem can be generalized for inverse Laplace transforms on linear paths and that the relative error of Contour-FFT is a regularized Gamma function. Two examples illustrate the modularity of the approach.
- 15:20 Scattering Analysis of Asymmetric Metamaterial Resonators by the Riemann-Hilbert Approach
- This work presents an analytical treatment of an asymmetric metamaterial-based resonator excited by an electric line source, and explores its beam shaping capabilities. The resonator consists of two concentric cylindrical material layers covered with an infinitely thin conducting shell with an aperture. Exact analytical solution of the problem is derived; it is based on the n‒series approach which is casted into the equivalent Riemann-Hilbert problem. The examined configuration leads to large enhancements of the radiated field and to steerable Huygens-like directivity patterns. Particularly, the directivities can be reshaped by changing the source location, as well as the extent of the aperture. The present results may provide alternative strategies for beam shaping and may contribute to development of novel nano-antenna designs.

Conveners: John L. Volakis and Christos Christodoulou

Room: DChair: John L. Volakis

- 14:40 Ultra-wideband Transceiver with High Interference Mitigation for Secure High Data Rate Communication
- We propose a new class of transceivers for secure communication and interference mitigation, operating over large bandwidths on the order of 10GHz. Specifically, a novel coding approach that combines frequency and code multiplexing is proposed. Equally important is power and hardware reduction by implementing a low power on-site coding with beamforming. The latter reduces power requirements for the digitizer by a factor of 8 to 32. In this paper, we present a description of the proposed high data system and integrated coding scheme. System performance is also evaluated in presence of interference and noise analysis is conducted to assess the impact of coding for different noise floors. Preliminary results show minimal degradation using orthogonal Walsh- Hadamard codes using ideal filters and a minimum digitizer resolution of 5 bits.
- 15:00 Advanced SARFID: a localization technique for UHF RFID tags
- In this paper a phase-based localization technique for UHF-RFID tags based on a synthetic-array radar principle is extended to an amplitude-phase processing. The technique flexibility is shown with reference to different scenarios, with either moving tags in front of a static reader antenna (inverse synthetic aperture radar principle) or static tags in front of a moving reader antenna (synthetic aperture radar principle).
- 15:20 Software Controlled Antennas for Cognitive Radio
- This paper presents the design of two antenna structures that are proposed for implementation in a cognitive radio environment. Such designs are software controlled and suitable for operation in a highly dynamic environment. The reconfiguration and automation of the two structures are discussed herein. The incorporation of such antenna structures on a software defined radio (SDR) platform is also presented.

Conveners: Stefano Maci and Timor Melamed

Room: EChair: Timor Melamed

- 14:40 Physical Optics versus Gaussian Beam Shooting for Shadow Field Analysis in High Frequency Regime
- Simulation of high frequency fields using Iterative Physical Optics and Gaussian Beam Shooting algorithms is studied. Particular attention is payed to the field evaluation accuracy in shadow regions. The accuracy is evaluated by comparing the results to those of numerically rigorous numerical methods.
- 15:00 Ray Series for Electromagnetic Waves in Static Heterogeneous Bianisotropic Dielectric Media
- We consider generally bianisotropic dielectric media. We consider the linear constitutive relations for bianisotropic media in the Boys-Post representation without spatial dispersion. We propose the high-frequency asymptotic ray series in terms of the magnetic vector potential. For the sake of simplicity, we assume that the media are static (do not change with time). In this case we can work in frequency domain, apply 3-D spatial rays, and avoid 4-D space-time rays. We assume that the media are so smoothly heterogeneous that we can apply the high-frequency ray-theory approximation. We assume the Weyl gauge (zero electric potential), which is best suited for electromagnetic wave fields. We derive the Hamiltonian function which specifies the rays and travel time. We then derive the transport equations for the zero-order and higher-order vectorial amplitudes.
- 15:20 Some New Techniques for Evaluating Sommerfeld Integrals for Microstrip Antenna Analysis
- A new transformation for evaluating Sommerfeld integrals is derived here when the path is deformed in the upper half of the complex plane. This transformation has the feature that as the lateral separation $\rho\to\infty$, the argument of the Bessel function diminishes. It is argued that this approach shall facilitate much efficient calculation of Sommerfeld integrals.

Conveners: Daniel Sjöberg and Ben Zion Steinberg

Room: BChairs: Daniel Sjöberg, Ben Zion Steinberg

- 16:00 Contact-free Measurement of Currents in Two-dimensional Parallel Conductors Using the Green Identity Approach
- The Green identity approach is used to reconstruct currents in very long parallel conductors above the ground from magnetic field data measured at some points under the conductors. By assuming that the conductor positions are known, this method can be used for contact-free measurement of currents in transmission lines in power system. This method gives the possibility of measuring high-frequency currents which cannot be measured with current transformers.
- 16:20 Comparison of Potential-Based Analysis Methods for Simple and Complex Media
- A comparison of vector and scalar potential formulations for simple and complex media is presented. Boundary conditions for the various formulations are provided, including new scalar potential boundary conditions valid for layered bianisotropic gyrotropic media. Advantages and limitations of each technique are discussed in order to identify the most suitable method of analysis for a given class of material.
- 16:40 Transverse Spin and Momentum in Structured Light: Quantum Spin Hall Effect and Transverse Optical Force
- I will give an overview of recent theoretical and experimental studies, which revisited fundamental dynamical properties of light: momentum and angular momentum. Recently, we described qualitatively new types of the spin and momentum in structured optical fields. These are: (i) The transverse spin angular momentum, which is orthogonal to the wave vector and is independent of the helicity and (ii) The anomalous transverse momentum, which depends on the helicity of light and exerts a weak optical force orthogonal to the wave vector. Both these quantities have attracted considerable attention and have been described and measured experimentally in various optical systems.
- 17:00 Scattering of lower order modes in a parallel plate waveguide loaded with a slightly deformed layer of conducting strips
- The lower order modes are derived for a parallel plate waveguide loaded with a sheet of parallel conducting strips. Using a first order perturbation method, we derive the scattering parameters due to a small deformation of the sheet. Results for scattering within and between the novel slow mode and the ubiquitous TEM-mode are presented. With increasing angle between the strips and the direction of propagation, the interaction between the slow mode and the deformation shifts downwards in frequency, due to the reduced phase velocity.
- 17:20 Tensor permittivity and permeability reconstruction of a one-sectional diaphragm in a rectangular waveguide
- This work is devoted to the solution of the inverse problem of reconstructing electromagnetic characteristics of anisotropic parallel-plane dielectric diaphragms. We consider a one-sectional diaphragm in a rectangular waveguide filled with anisotropic media having a diagonal permittivity and permeability tensors and propose a method of reconstructing the permittivity and permeability tensors from the values of the transmission coefficient at different frequencies.

Conveners: Jensen Li and Yang Hao

Room: CChairs: Jensen Li, Lauri Kettunen

- 16:00 Dispersion in spacetime transformation optics (Invited)
- The use of spacetime cloaking to hide events is an intriguing trick, but the unavoidable presence of dispersion limits the performance of any implementation, and needs to be accounted for. We show how the dispersion changes under transformation.
- 16:20 Microwave devices for controlling surface waves (Invited)
- In the last few years, great interest grown up in the control and manipulation of electromagnetic surface wave. The aim of this paper is to present a novel approach to design new devices able to manipulate them. To validate the proposed design, two structures, an all-dielectric device and a metasurface-based implementation, for surface wave cloaking will be presented and compared. Both devices show good performance in terms of wide bandwidth, polarization independence, and easy-to-fabricate. The proposed design methods offer great potential in a wide variety of practical application fields such as antennas, sensors, imaging and telecommunications.
- 16:40 Transformation optics with pseudomagnetic field (Invited)
- A real-space gauge field provides an alternative way in bending light by shifting the local dispersion surfaces instead of changing their shapes or sizes in conventional gradient index media. Here, we show that such gauge field can be realized by anisotropic metamaterials. A metamaterial structure with balanced electric and magnetic responses is designed to materialize such gauge field. By combining with transformation optics, it allows us to design spin-dependent optical devices. A unidirectional retroreflector is demonstrated as an example.
- 17:00 New methods for designing invisible and reflectionless materials (Invited)
- In this talk I shall treat wave propagation through a very simple system: an isotropic slab of material that changes permittivity over its cross section. I shall illustrate a method based on the application of complex spatial coordinates for designing inhomogeneous slabs that are invisible, or at least reflectionless from one side. As an extreme example I shall show that there exist `random' planar media with combinations of loss and gain that always have a transmission coefficient of unity. To conclude I shall suggest that metamaterials might be used to demonstrate a deep result that is seldom used in optics: the invariance of scattering for profiles `evolved' according to the Korteweg-de Vries equation.
- 17:20 Transformation Optics Applied to EELS (invited)
- Transformation optics is a relatively new subfield in electromagnetic research. Yet, it has been at the heart of many of the most promising advancements in electromagnetism in recent years. In combination with the metamaterial design, it has been widely used to realize exotic devices, such as invisibility cloaks or optical lenses with sub-diffraction-limited resolutions. Lately, transformation optics has entered the field of plasmonics. It has not only enabled the design of surface cloaks, beam splitters, and light harvesters, but also proven itself as an invaluable analytical tool in the study of complex plasmonic systems. In this contribution, we would like to add an entry to the already long list of fields where Transformation optics can make a difference, the study of electron energy loss spectroscopy of plasmonic nano-particles.

Conveners: Valentin Freilikher and Ehud Heyman

Room: DChairs: Valentin Freilikher, Ehud Heyman

- 16:00 Beam Summation Theory for Waves in Fluctuating Media. Part I: The Beam-To-Beam Scattering Matrix (Invited)
- We present a novel beam summation (BS) formulation for tracking wavefields in weakly fluctuating media. The overall strategy is to express the field in the medium as a discrete phase-space spectrum of beam waves, and to expand the local scattering excited by the interaction of each beam with the medium using the same beam set. Since the beams are localized in the spatial-spectral phase-space, the resulting beam-to-beam (B2B) scattering coefficients depend directly on the local spectral properties of the fluctuations, as a local alternative to the conventional plane wave scattering operator. This strategy is implemented by introducing the novel concept of propagating beam frame (PBF), a phase-space set of beam propagators that can be used as an overcomplete frame for a local expansion of the field and its interaction with the medium. This set constitute, in fact, a novel extension of the windowed Fourier Transform (WFT) frame. A key feature of this method is that it utilizes the same beam skeleton for all frequencies in the band. In this paper we derive this formulation and in particular we derive the closed form expressions for the B2B scattering matrix.
- 16:20 Beam Summation Theory for Waves in Fluctuating Media. Part II: Stochastic Fields (Invited)
- In Part I of this two-part paper we presented the "propagating beam frame" (PBF) concept, which provides a self-consistent framework for wave tracking through a fluctuating medium. The field is expanded using the BPF and the local scattering of each beam by the medium is re-expanded using the same beam-set and expressed as beam-to-beam (B2B) scattering coefficients. The entire scattering problem is thereby described in terms of the coefficients dynamics in the phase-space. In the present paper, we use the theory of Part I to derive a beam summation (BS) representation for the stochastic-field moments (observables) for cases where the medium fluctuations are expressed as a random process with given statistics. We derive closed form approximations for the stochastic B2B scattering moments, which are expressed in terms of the local spectral statistics of the medium projected on phase-space windows formed by the intersection of the excitation and the scattered beams. Since the medium statistics is typically smooth, unlike its realization, the resulting stochastic beam-to-beam (B2B) scattering matrix is compact and smooth. The stochastic observables are fully described in terms of the local dynamics of the B2B scattering moments as the wave propagates through the medium. It is demonstrated that the formulation computationally efficient and provides a compact representation for the scattering phenomenology.
- 16:40 Edge reflection-driven transition in transmission eigenvalue statistics in random media (Invited)
- We show both analytically and numerically that in quasi-one-dimensional (1D) diffusive samples the distribution of transmission eigenvalue (DTE) displays a phase transition as the asymmetry in the reflections of the sample edges increases. We also show numerically in 1D localized samples a similar transition, but in the distribution of resonant transmittance (DRT). These results reveal that rich physics arises from the interplay between edge reflection and the coherence of waves. This opens up new possibilities for controlling the transparency and the transmission eigenchannel structure of opaque media.
- 17:00 Neoclassical field theory for electromagneticly interacting elementary charges (Invited)
- We have constructed a neoclassical theory of electromagnetic interactions which features a new primitive scale - the size of free electron.
- 17:20 Propagation of Waves in Perturbed Periodic Waveguides (Invited)
- We provide a review of the main features of the wave propagation in one-dimensional periodic media subject to random perturbations. Using the transfer matrix approach we investigate the dependence of the Lyapunov exponent on the frequency and magnitude of the disorder.

Conveners: Karri Muinonen and Daniel Mackowski

Room: EChairs: Karri Muinonen, Daniel Mackowski

- 16:00 Capabilities of the Discrete Dipole Approximation for Large Particle Systems (Invited)
- The discrete dipole approximation (DDA) is a general method to simulate light scattering by arbitrary particles. This talk reviews the DDA with focus on its application to very large particle systems, typically consisting of large numbers of particles with sizes comparable to or larger than the wavelength. Overall, the DDA is a viable option for such problems - it is conceptually simple, can naturally handle arbitrary inhomogeneous particles, and benefits from the availability of open-source codes. However, the major limitation is the computational complexity rapidly increasing with the size of the system. A few ideas to alleviate this issue are discussed, including the fast multipole method and the multi-grid DDA. While the DDA is equally applicable to both connected and disconnected particle systems, when applied to the latter it provides some insights into the notion of multiple scattering.
- 16:20 Discrete Dipole Model of Scattering by Discretely Inhomogeneous Plane Parallel Media (Invited)
- A formulation and computational algorithm for directly simulating the electromagnetic wave reflection, transmission, and absorption properties of plane parallel layers of random particulate media, in which the characteristic size of the particles is comparable to the radiation wavelength. No assumption is made regarding the concentration of the particles; the application is specifically intended for the high particle concentration case characteristic of regolith, pigment layers, functional thin films, and so on.
- 16:40 T-matrix Simulations of a Collection of Scatterers for Validation of Numerical Electromagnetic Solvers
- This paper presents the use of the T-matrix method for a collection of scatterers for validation purposes of large-scale numerical electromagnetic scattering problems. In order to validate the simulation results for large geometries the T-matrix solution for a collection spheres and disks can be used. Scattering results using the T-matrix method, FDTD and MoM are compared. The results show that the T-matrix method for a small collection of scattering objects gives accurate reference solutions for large-scale scattering problems.
- 17:00 Validation of Radiative Transfer and Coherent Backscattering for Discrete Random Media
- Implementation of the multiple-scattering theory composed of radiative transfer and coherent backscattering (RT-CB) provides a method to compute scattering by large particulate media with reasonable accuracy and computing capacity. To validate the RT-CB code, scattering by varying spherical systems consisting of spherical scatterers beyond the Rayleigh regime are modelled with the multiple-sphere $T$-matrix method. By comparing the results using the phase function and the degree of linear polarization, we show that the RT-CB gives a valid approximation for low-density particulate media for the cases considered. Further improvements have to made in order to make the RT-CB code valid in dense random media. The RT-CB was recently translated to Fortran 90/95 and the code will be publicly available.
- 17:20 Multiple Scattering by Dense Random Media: Numerical Solution
- We study multiple scattering of electromagnetic waves in discrete random media of densely packed spherical particles. We conceptualize the scattering problem in terms of coherent and incoherent fields, focusing in on the ladder and cyclical interaction diagrams, and introduce wavelength-scale volume elements of particles as elementary scatterers. We describe a Monte Carlo radiative-transfer coherent-backscattering method for the approximate numerical solution to multiple scattering. Finally, we compare the results to exact computations using the Superposition T-Matrix Method and offer example computations for very large systems of particles.

Conveners: Ludger Klinkenbusch and Giuliano Manara

Room: BChairs: Ludger Klinkenbusch, Giuliano Manara

- 08:40 Bistatic Free-Space Measurements of Magneto-Dielectric Materials and Comparison with Numericals Models
- A bistatic field measurement apparatus is described. It enables to acquire the field scattered by magneto-dielectric samples. Two numerical models are also proposed, in particular a linear one, in order to simulate the field propagation in such an environment. Some comparisons between simulated and measured scattered field are presented for magneto-dielectric samples. This study is a prerequisite step for inhomogeneous magneto-dielectric characterization in free-space.
- 09:00 Directive Scattering by a Line Source Coupled to Infinite or Finite Electromagnetic Band-Gap Media (Invited)
- Radiation from a line source coupled to an Electromagnetic Band-Gap material is analyzed with two different methods. Using lattice sums technique combined with generalized reflection matrix method, the scattering from a crystal of infinite extension is rigorously investigated. The radiation from an electromagnetic crystal of finite extension is also solved with Cylindrical Wave Approach. The two methods show perfect agreement when the source is localized within the crystal, achieving a directive radiation. As a spacing between the two Electromagnetic Band-Gap layers is introduced, the finite structure analyzed with the Cylindrical Wave Approach shows significant edge diffraction at the boundaries. Agreement between results from the methods is recovered introducing a suitable layout of absorbers in the cavity.
- 09:20 The Energy Flow Structure During the Scattering of a Plane Electromagnetic Wave by a Magnetized Plasma Cylinder at Volume Plasmon Resonances
- The scattering of an obliquely incident H-polarized plane electromagnetic wave by a magnetized plasma cylinder is studied. It is assumed that the cylinder is located in free space and aligned with an external static magnetic field. The emphasis is placed on the case where the angular frequency of the incident wave coincides with one of the volume-plasmon resonance frequencies of the cylinder. The spatial structure of the energy flow patterns in the near zone of the scatterer is analyzed and the location of the regions with a greatly enhanced magnitude of the time-averaged Poynting vector is determined. It is shown that the sign reversal of the energy-flow component that is parallel to the cylinder axis can occur both at the surface of the cylinder and in its inner region.
- 09:40 Structuring Band-pass Dispersion with Cascaded High- and Low-pass Optical Metatronic Metasurfaces
- In the paradigm of optical metatronics, metasurfaces with multi-layered structures can be engineered to behave as multi-ordered filters for desired spectral dispersions, such as low-pass, high-pass, band-pass, and band-stop cases, following and inspired by electronic circuit design procedures. However, there is a constraint in the design of layered band-pass metatronic filters with narrow bandwidth. Based on the concept of metatronic metasurfaces, a new method is proposed to achieve optical band-pass dispersion by cascading a pair of metatronic high-pass and low-pass metasurface filters. The proposed method is also numerically validated in the higher-ordered band-pass filter design with sharper transition slopes to the stopband. The results of our numerical simulations illustrate the possibility for such multi-ordered optical band-pass filters with narrow bandwidth, augmenting the procedures for dispersion engineering using layered metatronic metasurfaces.
- 10:00 Leaky-Mode Characteristics of Silica-Substrate Supported Circular-Cylinder Silver Nanowire
- Waveguide modes propagating along the circular-cylinder silver nanowire on a silica substrate are calculated and studied using an in-house developed full-vector finite-element imaginary-distance beam propagation method (FV-FE-IDBPM). In particular, leaky-mode characteristics for the mode with field guided mainly at the top air-silver interface and that with field distributed mainly near the silver-substrate interface are presented and discussed based on high-resolution numerical analysis. Complex effective indices are accurately solved from which the modal propagation lengths are determined.
- 10:20 Web-based Application to Obtain the Propagation in Outdoor Environments Importing Data from OpenStreetMaps
- The implementation of a web-based application to obtain the propagation in outdoor environments is presented in this paper. The tool provides the results of an empirical formulation in a friendly user interface. The main advantage of the proposed system is that the data of the environment are obtained from OpenStreetMaps allowing the calculation at any part of the world with an easy accessibility to the required data. Moreover, the formulation is applicable to rural and urban environments. The web application has been implemented using HTML5 and CSS3. The open source JavaScript library Leaflet has been used to include interactive maps.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChairs: Georgi Nikolov Georgiev, Tsuneki Yamasaki

- 08:40 Induced Torsion Effects in Microwave Structures with Magnetoelectric Fields (Invited)
- At ferromagnetic-resonance frequencies, in small ferrite samples so-called magnetic-dipolar-mode oscillations can be excited. The near fields in vacuum, originated from a ferrite disk with these oscillations, are unidictional rotating fields. When a thin metal wire is placed above such disk, unique torsion-wave electric currents are induced. We analyze analytically these torsion effects. The torsion currents create the fields with unique topology. The results shown can be useful in development of microwave microscopy of chiral biological structures.
- 09:00 Condition for Phase Shifter Operation of the Circular Waveguide, Containing an Azimuthally Magnetized Ferrite Cylinder and a Dielectric Toroid (Invited)
- The condition for operation of the circular waveguide, loaded with a latching ferrite cylinder of azimuthal magnetization surrounded by a dielectric toroid, as a digital nonreciprocal phase shifter for the normal TE01 mode, is investigated. The complex Kummer confluent hypergeometric and real cylindrical functions formalism is applied. An iterative technique is elaborated, yielding the maximum value of the off-diagonal ferrite tensor element at which the structure provides differential phase shift. The influence of structure and material parameters on value mentioned and on the borderlines of the area of phase shifter operation is analyzed.
- 09:20 Increasing Effective Angular Resolution of Measuring Systems Based on Antenna Arrays (Invited)
- Resolution of goniometric systems on the basis of antenna arrays can be increased due to the secondary digital processing of the accepted signals. Necessary algorithms are created on the basis of solution to inverse problems.
- 09:40 Unifying Electromagnetic and Communication Theories: A Proposal for a New Research Program (Invited)
- The present paper will address the important but neglected aspect of the interrelationship between electromagnetic theory and communication systems. We propose a research program based on careful reconsideration of how the concepts `information', `energy', and `system' can be fruitfully generalized beyond their original matrix of use within the traditional domain of time-dependent signal analysis. Based on recent theoretical advances in the areas of near-field dynamics and electromagnetic system-theoretic methods, we outline the new approach based on first developing an electromagnetic information theory, then using the concept of information buried within the spatial structure of the field to elaborate a calculus that can be systematically deployed in order to study and develop general electromagnetic systems simultaneously in both space and time.
- 10:00 Evolution of the Quadratic Functions of the Time-domain Waveguide Fields (Invited)
- The quadratic field characteristics are derived in the class of real-valued functions of time for the circular waveguide. The evolutionary approach to electrodynamics is applied for the field analysis where Klein-Gordon equation plays a central role.
- 10:20 Pulse Responses of Plane Gratings in Dispersion Media (Invited)
- In this paper, we analyzed the pulse responses of plane gratings in the dispersion media by utilizing the parameters for permittivity properties of complex dielectric constants, and also investigated the influence of both dielectric and conductor by using the combination of the FILT method and PMM. And also, we confirmed the effectiveness and validity for present method compared with exact solution of perfect conductor plate in dispersion media.

Conveners: Paolo Nepa and Andrea Michel

Room: DChairs: Paolo Nepa, Andrea Michel

- 08:40 Implementation and Performance Evaluation of Graphene-based Passive UHF RFID Textile Tags (Invited)
- In this paper, we investigate the fabrication and wireless performance of graphene-based passive UHF RFID textile tags. Two different graphene-based inks were used to fabricate identical antennas on a fabric substrate by doctor blading technique. The performance of the tags was evaluated with wireless measurements throughout the UHF RFID frequency band. Based on our results, the graphene-based tags showed attainable read ranges of 1.6 and 2.4 meters. According to these first results, these tags have a great potential in future wearable applications along with cost-effective and eco-friendly aspects.
- 09:00 RFIDrone: Preliminary Experiments and Electromagnetic Models (Invited)
- We introduce in a unitary way the paradigm of radiofrequency identification (RFID) merged with the technology of Unmanned Aerial Vehicles (UAV) giving rise to RFIDrone devices. Such family comprises the READER-Drone, which is a suitable UAV integrated with an autonomous RFID reader to act as mobile scanner of the environment, and the TAGDrone, a UAV only equipped with an RFID sensor tag that hence becomes a mobile and automatically re-positioned sensor. We shows some handy electromagnetic models to identify the upper-bound communication performance of RFIDrone in close proximity of a scattering surface and we resume the results of some preliminary open-air experimentation corroborating the theoretical analysis.
- 09:20 Robustness of Wearable UHF-Band Ungrounded Antennas to Human-Body Proximity (Invited)
- Several wearable antennas suitable for implementation of UHF-RFID tags have been presented in the open scientific literature, showing a good robustness with respect to the body coupling effect, both on the input matching and on the antenna efficiency. In this work, a numerical investigation is presented in order to highlight that the robustness of the existing solutions for wearable, ungrounded, antennas can also be related to the distribution of the electric and magnetic energy densities close to the antenna borders.
- 09:40 Permittivity characterization based on Radar Cross measurements (Invited)
- In this paper, classical radar approaches such as the ones recently introduced for chipless RFID identifications are used for nondestructive permittivity characterization of a large variety of materials. A metallic resonant scatterer is placed on the material to be characterized and thanks to the acquisition of its resonant frequency the permittivity can be directly extracted with the use of classical formulas. Simulation and measurement results are presented to show the potential of this characterization technique and to validate the concept.
- 10:00 Encoding/Decoding Strategies for Frequency Domain Chipless RFIDs Employing Periodic Surfaces (Invited)
- This paper reviews the main features of chipless RFID tags realized with High-Impedance Surfaces. These tags, which comprise a periodic surface printed on top of a grounded dielectric slab, can be exploited in a number of encoding and decoding schemes. Several encoding methods have been investigated and the results are here analyzed and organized into a broad overview. In particular, the attention is devoted to the physical phenomenon at the basis of each design that is obtained by resorting to absorption, polarization conversion or polarization diversity.
- 10:20 Near-field Coupling in UHF-RFID Printer-Encoders
- In the framework of Near-field (NF) UHF-RFID applications, printer-encoder antennas represent an interesting scenario to investigate. In commercial RFID printer-encoders, the distance between the encoder and transponder antennas is typically a few millimeters only, and the encoder antenna has to reliably communicate with only one targeted tag among a number of tightly spaced transponders in very close proximity. In this paper, a number of encoder antenna layouts have been numerically analyzed in terms of power delivered to the transponder chip, by considering two commercial RFID tags. Moreover, the spatial selectivity of the encoder antennas is estimated. As a result, a reader antenna identical to the tag antenna is suggested as an optimal solution for meeting the severe requirement on the spatial selectivity of the encoding process.

Conveners: Francesco Andriulli and Pasi Ylä-Oijala

Room: EChairs: Francesco Andriulli, Pasi Ylä-Oijala

- 08:40 Volume Potential-Integral-Equation Formulation for Electromagnetic Scattering by Dielectric Objects (Invited)
- A volume potential-integral-equation formulation for electromagnetic scattering by dielectric objects is developed and discretized with fully continuous nodal basis functions. The equations are tested with either the point-matching or Galerkin's testing procedure. Galerkin's testing shows superior accuracy over the point-matching as well as over the standard discretization of the electric field volume integral equation with Schaubert-Wilton-Glisson (SWG) functions. The potential formulation is accelerated by the precorrected-FFT method.
- 09:00 Balanced tangential testing for the nonconforming discretization of the Electric-Field Integral Equation on open PeC surfaces (Invited)
- Recent attention has been devoted to the development of nonconforming implementations of the Electric-Field Integral Equation (EFIE), which impose no continuity constraints in the expansion of the current between adjacent facets. These schemes, based on the facet-oriented monopolar-RWG set, become more versatile than the traditional edge-oriented schemes, based on the RWG set, because they simplify the discretization around junctions in composite objects and because they can handle nonconformal triangulations. The existing nonconforming implementations tackle the numerical evaluation of the inherent hypersingular Kernel contributions of the EFIE by testing the fields over volumetric or surface domains attached to the boundary surface inside the conductor. Hence, the application of such schemes is restricted to closed PeC surfaces. In this paper, we present a novel nonconforming implementation of the EFIE that allows the scattering analysis of open PeC surfaces by testing the fields with a new, "balanced- tangential", strategy. We show for several examples of open PeC surfaces, infinitely long (2D) or arbitrarily shaped (3D), that the proposed scheme provides similar or slightly better accuracy than the RWG-discretization of the EFIE and same meshing.
- 09:20 A Full Wave Conductor Modeling Using Augmented Electric Field Integral Equation (Invited)
- A numerical full wave solver is proposed to solve conductor problems in electromagnetics. This method is an extension of the dielectric augmented electric field integral equation (D-AEFIE). Using this method, conductors, from lowly lossy to highly lossy, can be rigorously modeled to capture the conductive losses. Broadband stability can be achieved, thanks to the introduction of the augmentation technique. This paper demonstrates the formulation of this method. A simple and effective preconditioner is introduced to accelerate the convergence. A novel integration scheme is adopted to accurately capture the losses inside the conductor. Finally some numerical examples are shown to support the capability of this method to solve real-world circuit problems.
- 09:40 Fast Integral Equation Method for Metasurface Antennas (Invited)
- In this paper, we describe an efficient method for the full-wave simulation of printed antenna designed by means of metasurface (MTS) concept, where the texturing is realized by elliptical patches. The method is based on the fast solution of integral equation discretized by using the method of moment (MoM). The two-dimensional version of the Fast Multipole Method (FMM) is introduced to accelerate the solution of the linear system derived from the full-wave analysis method. Numerical results are provided to demonstrate the validity of the proposed approach.
- 10:00 Novel Single-Source Integral Equation in Electromagnetics (Invited)
- New single-source integral equation (SSIE) of computational electromagnetics has been recently proposed. Unlike the previously known SSIEs which are derived from traditional surface integral equations (IE) through elimination of either electric or magnetic equivalent current, the new SSIE is obtained from the volume IE stated for homogeneous objects. Thus far, the novel electric field SSIE has been demonstrated to be applicable to the problems of magneto-quasi-statics with both homogeneous and layered medium background. It has been also successfully applied to both the scalar and vector problems of full-wave scattering on homogeneous penetrable 2D scatterers. This paper overviews the novel SSIE and problems to which it has been successfully applied to.
- 10:20 Performance of Iterative Solvers in the Discrete Dipole Approximation
- The discrete dipole approximation (DDA) is a variant of volume-integral equation method, which speed largely depends on the iterative solution of system of linear equations. I systematically studied the performance of this solution, varying the particle refractive index, DDA formulation (including non-standard ones), and several Krylov-subspace iterative solvers. For that I used publicly available ADDA code, so the conclusions can be directly employed by the practitioners of the DDA. Apart from the expected strong dependence on the refractive index, the number of iterations significantly differs between the DDA formulations, especially for purely real refractive indices. For small particles the number of iterations versus refractive index can be estimated by a simple relation, previously derived from analysis of the spectrum of the interaction matrix.

Conveners: Ari Sihvola and Henrik Wallén

Room: BChair: Henrik Wallén

- 11:00 Teaching experiment in Aalto University: progressive inquiry, reverse engineering, and company collaboration in a hands-on antenna course
- We describe a teaching experiment conducted in a hands-on antenna course in Aalto University. The course was specifically designed to fulfill the higher-level (senior master's and post-graduate) educational objectives and it was implemented by applying the principles of the "progressive inquiry" model. The model was introduced and applied in two practical assignments, giving special emphasis in skills such as group cooperation and expertise development within realistic scenes, i.e., reverse engineering and collaboration with a company.
- 11:20 Algebraic Electromagnetism
- This paper introduces the concept of Algebraic Electromagnetism to solve the problem of finding stable spatial discretizations of the electromagnetic field for large scale, ultra-wide-band electromagnetic systems, composed of possibly nonlinear subsystems with memory and/or hysteresis effects. It is a thorough approach to exact discrete electromagnetism, given by an algebraic construction of general material operators that have the property that solving Maxwell's equations with these is exactly equivalent to solving a corresponding system of ordinary differential equations.
- 11:40 Electromagnetism and Cross-disciplinary Problems
- Electromagnetic theory is a model of the electromagnetic phenomenon. As is well known, the model can be expressed in many different ways. All the formulations are, however, concretizations of the same so-called "abstract general" of electromagnetism. In this paper we consider the Maxwell house as this abstract general. The motivation for this is, an increasing amount of progress in engineering science takes place on the interfaces between different fields. Cross-disciplinary results are best achieved by formalising first the logical reasoning behind electromagnetism, as this then results in an unambiguous basis for cross-disciplinary communication.
- 12:00 Identifying trends of an International Master's level Electromagnetic Course: Assessment of an in Class Conceptual Survey and Homework Assignments
- In this work the extraction and evaluation of student's aptitude of a master's level, electromagnetics class (Fall 2015) at Aalto University has been done using both pre- and post-course conceptual tests and homework assignments. Several qualitative results obtained, mostly revealing trends in certain areas of electricity and magnetism. An almost linear trend regarding the pre- and post-test results is extracted, while a correlation scheme between homework scores and student's learning gain is obtained. These results might be used for both educational and statistical purposes, asserting the overall educational process with tools and knowledge towards properly designed courses and student oriented electromagnetics pedagogy.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChairs: Magdalena Salazar-Palma, Tapan Sarkar

- 11:00 Breach of Electromagnetic Symmetries in Particle Arrays (Invited)
- We describe several basic schemes for magnetization-based strongly non-reciprocal plasmonic particle arrays. Examples of periodic arrangements are discussed and presented as special cases of a more general Frieze-group symmetry framework. Quasi-periodic particle arrays are discussed as well, and their support of non-reciprocity is explored. The manifestation of strong non-reciprocity in the fractal spectrum of quasi-periodic arrays is presented.
- 11:20 Fredholm Integral Equations: Scattering on Dielectric Structures (Invited)
- We consider volume singular integral equations (VSIEs) which describe electromagnetic scattering on 3D inhomogeneous dielectric structures. By using the theory of multidimensional integral equations we reduce VSIEs to the Fredholm integral equations of the second kind.
- 11:40 On Multi-Dimensional Systems; Properties of their Transfer Functions (Invited)
- A range of interesting electromagnetic systems like antennas, extraordinary transmission and absorbers have been shown to have certain bandwidth limitations given by a family of sum-rules. Common for the systems are that they are passive, linear and time-translational invariant. In this paper we shortly review the extension from one-dimensional passive systems to multi-dimensional systems, aiming towards constraining the system properties. The most well-known case of system constraints follows from multi-dimensional passivity, where a Schwartz-kernel representation theorem maps Borel-measures with a growth condition to the (complexified) Fourier transform of the transfer function. A weaker form of system constraints follow from generalizations of Kramers-Kronig relations. One such approach is a generalized Cauchy-Bochner representations, under Sobolev space limitations on the transform pair. This approach is closely connected to that the support of the transfer function is within an acute cone. Another approach to system transfer constraints is the multi-dimensional Hilbert-transform, often with square-integrable function requirements. It is observed that the Cauchy-Bochner representation and the multi-dimensional Hilbert transform yield different representations in higher dimensions although they give the same in one dimension. We end the paper with a few explicit examples of functions that satisfy the constraints.
- 12:00 A Numerically Stable Algorithm for Eccentrically Metamaterial Covered Circular Cylinders (Invited)
- The regularization for monochromatic TM/TE-z polarized waves scattering from multiple non intersecting circular penetrable boundaries has recently been proven to be a requisite for its stable numerical implementation for a wide scope of parameters. The validity and necessity of corresponding regularization algorithm will be demonstrated for medium parameters which are from a double negative (DNG) material media. The preliminary numerical results which already prove the properties mentioned above are given in this paper.

Conveners: Hendrik Rogier, John Volakis, Sam Agneessens and Asimina Kiourti

Room: DChairs: Hendrik Rogier, John L. Volakis

- 11:00 Conductive Textiles for Wearable Electronics (Invited)
- We present a new class of conductive textiles, already demonstrated for a variety of flexible antennas and integrated wireless devices. Our approach is based on silver-coated polymer filaments that are bundled in groups of 7s to 600s to form commercial threads (E-threads) for use in regular embroidery machines. Doing so, we have been able to create any shape or form of a surface on a garment with geometrical precision as high as 0.1mm. If needed, our conductive surfaces can be colorful, and further integrated with flexible polymer substrates. Importantly, their conductivity is as good as that of copper, even after rough treatments. Overall, this technology brings forward several new possibilities for wearable electronics.
- 11:20 Enhancing the Design of Textile Antennas with a Polynomial Chaos-based Stochastic Framework (Invited)
- A stochastic framework is presented to enhance the design of textile antennas, by addressing the impact of production uncertainties, substrate bending and compression on the performance of textile antennas. Each effect is considered separately and the probability density functions corresponding to the design parameters undergoing variations are experimentally estimated. In order to accurately quantify the statistical distribution of the antenna's figures of merit corresponding to these variations, we introduce a stochastic collocation method based on a generalized polynomial chaos technique or on Pade' approximants.
- 11:40 Design Considerations for Wearable Antennas (Invited)
- With the development of generalized connectivity and the increased use of Body Area Networks, wearable antennas have become ubiquitous in the last decade. Their design presents a challenge, as they per definition are located at the interface between free space and an environment which is intrinsically lossy and hostile to the efficient radiation of electromagnetic waves. In this contribution, we propose a theoretical analysis of different canonical sources placed on biological tissues. Based on the insight gained, several simple design rules will be proposed and illustrated on a practical antenna design.
- 12:00 Dual Band Implantable Antenna for Biomedical Applications
- In this paper, a dual band implantable microstrip antenna is introduced for MICS and ISM band biomedical applications. The main radiating layer of the antenna consists of a small rectangular patch which is designed by etching three complementary split ring elements. Also, a shorting pin inserted between the patch and ground plane is used for the antenna miniaturization. The dimension of the antenna fed by a vertical probe is only 14×14×1.27 mm3. The proposed complementary split-ring implantable antenna (CSRIA) provides 20% and 6% impedance bandwidth at the respective bands and exhibits uniform radiation patterns at each frequency band. Analysis and design of the proposed antenna is carried out by means of two simulators, namely Ansoft High-Frequency Structure Simulator (HFSS) and CST Microwave Studio. In the paper, numerical results for the proposed design are presented.

Conveners: Ursula van Rienen and Revathi Appali

Room: EChairs: Revathi Appali, Michael J Havrilla

- 11:00 Dipole forward simulation guides transcranial electric stimulation of the hand knob area (Invited)
- Transcranial electric stimulation (TES) is a non-invasive technique driving small currents to the brain to modulate neuronal activity. Applications of TES in therapy of neurophysiological disorders require implementations of focused TES to specific target areas in the brain. We introduce a new technique based on the idea of reciprocity, where targeted TES is guided by resampling electric field features originating from an electric current dipole in the target area. We compute the current density in the brain and the electric scalar potential on the scalp surface of a volunteer produced by a dipole in the target area. The resulting minima of the current density distribution are used to guide a bipolar TES stimulation. The maximum and minimum of the potential on the scalp surface serve for polarity selection of the TES electrodes. We compare our results to those obtained with a distributed beam former TES simulation for the same target area. We found that the beam former based TES produced the maximum of the current density in a different brain area than the target area, while our new method produced the maximum at the target area. In the target area, the beam former based TES produced a factor 3 lower current densities than our new method. Our new approach provides a simple means for guiding targeted TES in clinical studies.
- 11:20 Challenges in Modeling Nerve-Electrode Interactions of Neuronal Implants (Invited)
- This paper accompanies a tutorial on challenges in modeling of nerve-electrode interactions in the context of neurochips and cochlear implants. We highlight on the biological processes that needs consideration in modeling the extracellular phenomena and their interaction with the electrodes. We first emphasize on the importance of mathematical models in abstracting the biological phenomena of nerves. Secondly, we show how a multi-physical approach is needed in these mathematical models. Finally, we take up an example of cochlear implant to demonstrate the importance of several features that needs consideration in modeling.
- 11:40 Improved Result for the Refractive Index of Human Hemoglobin Solutions by Kramers-Kronig Relations
- Applying Kramers-Kronig relations we compute the real part of the refractive index of aqueous solutions of human hemoglobin from its absorption spectra in the range 250 nm-1100 nm. Since the solution's absorption is not limited to this spectral range, strong ultraviolet (UV) and infrared absorbance of the water have been considered in previous investigations [Sydoruk et al., J. Biomed. Opt. 17(11), 2012]. We improve these results regarding the concentration-dependent absorption of water, the UV absorbance of hemoglobin's peptide-backbone, and by fixing the remaining unknown parameters via a global fit.
- 12:00 Evaluation Method for In-situ Electric Field of Different TMS Coils in Human Brain
- This study proposes a method to evaluate focal stimulation in the target area of the brain for non-invasive electro-/magneto-stimulation. The feasibility of three different coils used in transcranial magnetic stimulation (TMS) is considered for clinical applications. In the second part, we investigate the induced electric fields in the brain using ten individual anatomically realistic models of the head. The group-average electric fields are studied using a registration procedure to map each individual's brain to the standard brain space. From computational results, it is difficult to localize the induced electric field in the target area of the brain due to the morphological variability of the human brain, at least for the coils considered herein. The evaluation method proposed is useful for future design of the coils.

Topological Photonics in a Continuum

Mário G. Silveirinha

Room: BChair: Lianlin Li

- 13:40 Topological Photonics in a Continuum (Plenary)

Conveners: Cristina Ponti and Andrea Randazzo

Room: BChairs: Andrea Randazzo, Giuseppe Schettini

- 14:40 Rigorous Analysis of Light Scattering by a Grating of Nanocylinders Coupled to a Dielectric Substrate (Invited)
- Light scattering by a grating made of the Ag nanocylinders onto a dielectric substrate is investigated using an accurate and rigorous formalism based on a recursive algorithm combined with the lattice sums technique. Physical insight is given to the localization of the field along the interfaces of the Ag nanocylinders, to the strong reflected field by the grating and the field enhancement at the surface of the dielectric substrate. The accuracy of the numerical analysis has been validated based on the principle of the energy conservation.
- 15:00 Accurate Formulation of Electromagnetic Scattering from Dielectric Slab Including Periodic Circular Cylinder Array with a Heterogeneous Cylinder (Invited)
- This paper considers the two-dimensional electromagnetic scattering problem of a dielectric slab including a periodic circular cylinder array, in which one cylinder is replaced by a different cylinder, and presents a spectral-domain formulation. The formulation is based on the recursive transition-matrix algorithm and the pseudo-periodic Fourier transform, and the wavenumber sampling is introduced in the Brillouin zone.
- 15:20 Long-Wave Approximation for the Effective Dielectric Tensor of Periodic Materials
- We describe a method to calculate the effective dielectric tensor of a periodic array of dielectric cylinders embedded in a host matrix for transverse electromagnetic waves whose wave length is much lager than the distance between the cylinders. We represent the field and the effective tensor as a power series in terms of a small parameter proportional to the field frequency and reduce the problem to a system of recurrence equations. For regular lattices we provide an explicit formula for the effective tensor which is in very good agreement with numerical computations in considered examples.

Conveners: Kazuya Kobayashi and Yury Shestopalov

Room: CChair: Martin McCall

- 14:40 Wiener-Hopf Analysis of the Diffraction by a Thin Material Strip (Invited)
- The plane wave diffraction by a thin material strip is analyzed using the Wiener-Hopf technique and approximate boundary conditions. An asymptotic solution is obtained under the condition that the strip width is large compared with the wavelength. Applying the saddle point method, the scattered far field is evaluated asymptotically. Numerical results on the radar cross section (RCS) are presented.
- 15:00 A Well-Conditioned, Hermitian, Positive Definite, Combined Field Integral Equation for Simply and Multiply Connected Geometries (Invited)
- We present a new preconditioner for the combined field integral equation (CFIE) that gives rise to a Hermitian, positive definite system of linear equations. Differently from other Calderon strategies, this scheme necessitates a standard discretization of the electric field integral equation (EFIE) with Rao-Wilton-Glisson (RWG) basis functions (i.e., no dual EFIE matrix required), is free from spurious resonances, and is stable down to the static limit for both simply and multiply connected geometries. The fact that the new system matrix is Hermitian, positive definite, and well-conditioned makes it amenable for fast iterative and direct solvers. Numerical results demonstrate the effectiveness of the proposed approach
- 15:20 A Floquet Wave Theory for Curvilinear Locally Periodic Boundary Conditions (Invited)
- In this paper, we discuss an extension of the Floquet-wave theory to curvilinear locally periodic boundary conditions. The local periodicity of curvilinear impedance surfaces is exploited to adiabatically apply the Floquet Wave theorem to fields and currents. We show that this extension allows for a good description of the interaction between the currents and the curvilinear boundary conditions. Based on this, it is possible to set an efficient design procedure for modulated metasurface antennas. Numerical results are provided to demonstrate the validity of the proposed approach

Conveners: Paolo Nepa and Andrea Michel

Room: DChairs: Andrea Michel, Paolo Nepa

- 14:40 EM Analysis of Smart Shelf RFID Antenna with Reconfigurable Interrogation Zone (Invited)
- This paper presents the design and EM analysis of a near-field RFID antenna for the smart shelf applications where spatially-reconfigurable interrogation zone is required. Antenna operation is based on the EM coupling between the open-ended or shorted microstrip (MS) feed line and parallel planar metal strips printed on top of a dielectric layer. The novelty of the proposed design corresponds to utilizing the RF switches altering the length of meander MS line and thus changing the phase distribution of the radiating antenna elements. Near-field distributions calculated in the planes parallel and normal to the antenna surface illustrate the mechanism of extending an area of strong E-field necessary to activate multiple RFID tags.
- 15:00 Object Attitude Estimation Using Passive RFID Tag Arrays (Invited)
- A technique to estimate the attitude of an object using RFID tags is presented in this paper. The approach is based on the application of MUSIC algorithm to the phase measurements of an array of RFID tags attached to the object. The cost and infrastructure of the system is minimized since a single transmitter antenna is required. The performance of this technique was validated through simulations and measurements in an anechoic chamber. Results showed that the estimated attitude accuracy is within the uncertainty margin of the RFID reader employed in wide angular range. In addition, the calibration of the array turns out to be critical in order to reduce errors mainly caused by the difference between the effective separation between RFID tags and its expected value.
- 15:20 RFID Tags for In-Situ Tire Monitoring (Invited)
- A broadband and flexible UHF RFID tag designed to overcome the challenges of placement in tires is presented. The tag antenna design is discussed and its performance is evaluated through read-range, threshold and stretch tests. Next a smart sensing and logging capable EPC Class-1 Gen-2 compliant UHF RFID prototype tag board is presented to demonstrate the feasibility of RFID sensors in tires.

Conveners: Ursula van Rienen and Revathi Appali

Room: EChair: Revathi Appali

- 14:40 Sub-Voxel Refinement Method for Tissue Boundary Conductivities in Volume Conductor Models
- The resolution and element type of the mesh used in finite element method modelling of tDCS affect greatly on both the accuracy of the solution and computation time. Usually tetrahedral meshing is used in these models as they approximate curvature well but they are slow to solve. Using a voxel grid as the mesh reduces the computation time significantly but the cubical elements are not the most suitable option for curved surfaces. Tissue boundaries can be modelled as a layer of voxels with an average conductivity of the surrounding tissues. However, as the boundary being modelled only rarely divides a voxel into two equally sized portions, this approach is often erroneous. In particular with low resolutions. In this paper we propose a novel method for improving the accuracy of anatomically correct finite element method simulations by enhancing the tissue boundaries in voxel models. In our method, a voxel model is created from a set of polygonal surfaces segmented from MRI data by first voxelizing with a fine resolution and then increasing the voxel size to wanted resolution and calculating the ratio of fine voxels in- and outside the surface within each coarse voxel. Thus a more accurate proportions for the volume of a coarse voxel inside and outside the tissue boundary is achieved and its conductivity can be better approximated. To test the performance of this method, a series of simulations of motor cortical tDCS were performed using resolutions from 0.2 mm to 2 mm scaled to 0, 2 or 4 times finer resolution. Based on the results, the voxel size can be doubled with a cost of 3% in relative error by using our method and thus the modelled DOFs can be decreased by 87% and the simulation times decreased by 82%.
- 15:00 A Physical Model of Blood Platelets Shape and its Effect on Light Scattering
- Quantitative description of blood platelet shape and its dramatic change during activation is necessary for the correct interpretation of light-scattering data, routinely measured in diagnostic laboratories. We propose the model of platelet shape, based on the known information on the cell cytoskeleton. The model geometry is characterized by two parameters: the volume and the overcurvature of the internal microtubule bundle, which changes during platelet activation. We describe the procedure for the construction of a cell shape given the volume and overcurvature, and also discuss the simulation of light scattering by such objects.
- 15:20 A Novel Wide-Band Reflection-Based System for Measuring Abdominal Fat in Humans
- A Wide-Band (WB) radio frequency (RF) system has been thoroughly developed in order to measure the Subcutaneous Fat (SF) thickness in the abdominal region of humans. Recent conducted research has shown that the SF thickness is related to the thickness of internal fat called Visceral Fat (VF), which has important health implications, and therefore cannot be measured accurately by non-invasive techniques. Thus, this proposed non-invasive RF system offers the possibility of measuring the SF thickness and then estimating the VF thickness. The investigation details work carried out to optimise the penetration depth and the range resolution. These considerations resulted in a Gaussian pulse with a 1.45 GHz centre frequency and 462 MHz bandwidth being selected for the system. This has been implemented using an accurately designed compact antenna based on double-ridge horn (DRH) inside a high-permittivity material, which has been designed using the CST Microwave Studio (MWS) software. The employed abdominal model consisted of three layers: skin; fat, and muscle. The WB pulse has been directed at the model, and the reflections recorded for several SF thicknesses, including an infinitely thick layer, which provided the reference system pulse to compare the other cases with. This successfully demonstrated the principles of the system operation, with SF thickness of 10 to 30 mm being accurately measured, based on amplitude variations and also time shifting, in the proposed RF system.

Conveners: Cristina Ponti and Andrea Randazzo

Room: BChairs: Andrea Randazzo, Mats Gustafsson

- 16:00 Reflection, transmission and absorption coefficients of a dusty plasma slab
- The reflection, transmission, and absorption coefficients of a dusty plasma slab at terahertz frequency are simulated using the shift operator finite-difference time-domain (SO-FDTD) method. The problem which incorporates both frequency dispersion and dust particles' contribution is solved for the electromagnetic waves propagation in dusty plasma. The numerical verification of the approach is performed by comparing with the numerical results in reference. The computed results show that terahertz waves may have the potential application in the plasma diagnostics and blackout communication.
- 16:20 Broadband Power Transfer Through a Metallic Wire Medium Slab
- The work contains an experimental confirmation and a theoretical study of broadband power transfer in wire medium slabs. The motivation of this work is a set of novel thermophotovoltaic devices suggested earlier. The key element of these devices is a wire medium slab which electromagnetically connects hot and cold parts without touching them due to a small gap between the ends of the wires and these parts of the system. The electromagnetic connection implies radiative heat transfer. This transfer presumably holds in a very wide band of infrared frequencies. However, this theory was never confirmed experimentally. Even the conceptual possibility of broadband electromagnetic power transfer through a wire medium layer was obtained only in numerical simulations. In the present work, the authors propose a test-bed system, qualitatively mimicking the radiation by a thermal emitter in the radio frequency range. The thermal emitter is replaced by an input waveguide and the photovoltaic (cold) part -- by an output waveguide. They are separated by a substantial air gap in which an array of parallel wires is introduced, not touching the waveguide walls.
- 16:40 Recent Advancements in the Forward Scattering with the Cylindrical Wave Approach
- The Cylindrical Wave Approach is a numerical-analytical technique for the simulation of forward scattering by buried cylindrical targets. Such a technique implements the cylindrical-wave expansions to deal with the scattered field by circular cross-section cylinders in different environments. The method is capable to solve reflection and transmission from flat or slightly rough boundaries, through suitable cylindrical waves of expansions. Therefore, targets may by buried under an interface or placed in a stratified medium, with a high flexibility in the simulation of possible scattering scenarios. Applications are in the buried object detection and localization through electromagnetic techniques.
- 17:00 Waveform Design for Dispersive SAR
- Electromagnetic pulses that travel through dispersive and lossy material may change their shape and lose a significant amount of energy. This distortion complicates imaging through dispersive and lossy material. Waveform design is one aspect to consider when trying to improve imaging capabilities. In this paper, an analytic expression for a precursor waveform is derived for SAR imaging. Precursor waveforms have been proposed as those waveforms that experience minimal decay and hence, are ideal for imaging in dispersive media. This precursor waveform is compared to the optimal waveform of Varslot, et al. obtained by numerical methods.
- 17:20 Numerical Solution of Scattering Problems on 2-D and 3-D Objects Buried under Locally Rough Surfaces by Buried Object Approach (Invited)
- In this work, the implementation of the buried object approach (BOA) to two-dimensional (2-D) and three-dimensional (3-D) scattering problems related to bodies buried under locally rough surfaces is discussed. BOA method is based on treating the irregularities forming rough surface as buried dielectric objects. In this way, it subtly incorporates the impact of the roughness to an electric field integral equation (EFIE) whose solution gives the scattered field. Then, this EFIE is solved by using method of moments (MoM). BOA method can be applied both 2-D and 3-D scattering problems of buried object under 1-D and 2-D rough surfaces, effectively. Various numerical results will be presented to demonstrate the applicability and effectiveness of this approach.

Conveners: Jensen Li and Yang Hao

Room: CChairs: Jensen Li, Gerhard Kristensson

- 16:00 The Limits and Extension of Transformation Optics (Invited)
- We explore an apparent limitation of transformation optics, namely that a given transformation induces polarization-dependent impedance gradients that might lead to scattering. This observation must be reconciled with the idea that the transformation optics algorithm is `exact', and leads to perfect morphing of the electromagnetic field without inducing scattering. We also discuss the role of curvature in transformation optics, showing that the conventional algorithm is nothing other than an interesting re-representation of flat Cartesian (Minkowskian) space (spacetime), without any curvature. However, we also consider possible extensions to transformation optics, to schemes that embrace curvature, and include so-called anholonomic transformations. We also show that the conventional spatial transformation optics algorithm can locally be described by six numbers.
- 16:20 Broadband Metasurface for Surface Wave Lenses (Invited)
- This paper presents the design of a metasurface that exhibits glide symmetry. This allows the metasurface to support a mode that is confined to the surface for a broad band of frequencies. In addition it is shown that the mode index of such surfaces depends only weakly on the frequency over a given range. We then propose these structures as a practical solution to the fabrication of broadband surface-wave lenses designed using quasi-conformal transformation optics technique.
- 16:40 Open cloak designed with transformation optics (Invited)
- In this letter, we propose an object independent open cloak design to conceal any object at a distance. The proposed idea is based on the multi-folded transformation optics to provoke the remotely design of a hidden region, which is open to the outer world. Such obtained hidden region has no influence to the outer boundary scattering field; also, no EM waves can penetrate into such hidden region. The simulation results clearly verified the expected cloaking behavior of our proposed device for various hidden object's shapes and types.
- 17:00 Flat Transformation Optics (Invited)
- This paper presents an approach for the analysis of surface-wave (SW) propagation on modulated surface impedance described through a 2-D coordinate transformation. This approach is based on an extension of geometrical optics (GO) description for plane waves in graded index materials to SWs supported by modulated, impenetrable isotropic or anisotropic impedance boundary conditions. In particular, it extends to SWs the basic concepts of GO (ray-path, ray-velocity, transport of energy), thus, resulting in an elegant formulation which allows for close-form analysis of planar operational devices. Furthermore, being the modulated surface impedance based on 2-D coordinate mapping, it allows one to determine ray path without resorting to ray tracing.

Room: D

Chairs: Ismo V Lindell, Juan R Mosig

- 16:00 Simulations and Measurements of Large Phase Progression in Multi-layered Metamaterials
- Insertion phase in multi-layered metamaterials play an important role in understanding the constitutive parameters of the material. Simulations and measurements show the distinct large phase change across the frequency band in which the metamaterial exhibits special parameters. This paper addresses the phase behavior for materials that use loops or rings for magnetic properties and rods, wires, or probes for electric properties. Continuous wires and cut wires in the structure show different properties, especially in the frequency regions where negative refraction occurs. The conjecture that negative refraction is a manifestation of insertion phase variations is reiterated in this paper.
- 16:20 Selected features of metamaterials with near-zero parameters
- Metamaterials with near-zero parameters exhibit unique features that enable the exploration of qualitatively different physics in classical and quantum electrodynamics. In our presentation, we will present a review of some of the most relevant phenomena and our ongoing efforts in this area. In particular, we will emphasize the geometry-invariant properties that arise from the decoupling of spatial and temporal field variations, leading, for example, to the excitation of bound states whose eigenfrequency is independent of the geometry of the external boundary. We also specifically address the reversible decay dynamics experienced by a two-level system coupled to these bound eigenmodes, even under the deformation of the external boundary of the cavity.
- 16:40 A Polarization-Independent Single Band Switchable Metamaterial Absorber
- In this paper, a single band switchable metamaterial absorber based on active frequency selective surface (AFSS) has been presented. The proposed design comprises of periodically arranged circular loops on which semiconductor switches (PIN diodes) are implemented. By controlling the bias voltage of the PIN diodes, the absorption frequency can be switched between two different frequency bands. Moreover, the proposed design is four-fold symmetric thereby realizing polarization-insensitive behaviour, unlike the earlier reported switchable absorbers. Finally, the structure has been fabricated, whose measured results are in good agreement with the simulated responses under normal as well as oblique incidence.
- 17:00 Electromagnetic wave propagation in metamaterials: a visual guide to Fresnel-Kummer surfaces and their singular points
- The propagation of light through bianisotropic materials is studied in the geometrical optics approximation. For that purpose, we use the quartic general dispersion equation specified by the Tamm-Rubilar tensor, which is cubic in the electromagnetic response tensor of the medium. A collection of different and remarkable Fresnel (wave) surfaces is gathered, and unified via the projective geometry of Kummer surfaces.
- 17:20 Numerical Investigation of DB Metamaterial and Retrieval of its Effective Parameters
- DB boundary conditions require vanishing of normal components of electric and magnetic flux density vectors on the boundary surface. In this paper, we present a free-space simulation analysis of the unit-cell structure proposed for the realization of a metamaterial exhibiting DB boundary conditions. From numerically calculated reflection and transmission parameters all components of the effective permittivity and permeability tensors, characterizing the DB material, are retrieved both in the axial as well as in the orthogonal directions to the metamaterial boundary. Such effective constitutive parameters are extracted using S-parameter inversion technique for obliquely incident wave.

Conveners: Francesco Andriulli and Pasi Ylä-Oijala

Room: EChairs: Pasi Ylä-Oijala, Francesco Andriulli

- 16:00 Singular Integral Equations in the Wave Scattering Problems
- The problem of reflection of a plane 3D electromagnetic wave by an irregular boundary containing a locally inhomogeneous well conducting section is considered. The boundary value problem for the system of Maxwell equations in an infinite section with an irregular boundary is reduced to the solution of systems of singular equations in case of the E or the H polarization. A numerical algorithm for their solution is developed. Results of calculation of reflected field patterns are presented.
- 16:20 Characteristic Mode-Surface Integral Equation Analysis of Plasmonic Nanoparticles (Invited)
- The theory of characteristic modes (TCM) is applied to analyze optical properties of plasmonic nanoparticles. TCM gives excitation independent characteristic solutions of the electromagnetic problem formulated with surface integral equations and can provide additional information of the plasmonic resonances that can be difficult to obtain with conventional electromagnetic field analysis methods.
- 16:40 Unequally-spaced fast Laplace transform for Green's function evaluation
- A fast method for the radiation problem of arbitrary oriented plane is presented. It combines an adaptative spectral integration scheme and a recently proposed unequally-spaced fast Laplace transform algorithm [F. Andersson, "Algorithms for Unequally Spaced Fast Laplace Transforms," Applied Computational Harmonic Analysis, vol. 35, pp. 419-432, 2013]. It is illustrated on the free-space Green's function through an example where a speed-up factor of 2-3 orders of magnitude is evaluated compared to the brute force spectral integration.
- 17:00 Theory of a Loop Antenna Located on the Surface of a Dielectric Column in a Magnetoplasma
- The electrodynamic characteristics of a circular loop antenna located coaxially on the surface of a dielectric column in a magnetoplasma are studied using the integral equation method. The antenna is excited by a time-harmonic voltage and represents an infinitesimally thin, perfectly conducting narrow strip coiled into a ring. The column axis is assumed to be aligned with an external static magnetic field. The problem is reduced to a system of integral equations for azimuthal harmonics of the antenna current. Using the singular properties of the kernels of the integral equations derived, the current distribution and input impedance of the antenna are found and analyzed in the case where the surrounding magnetoplasma admits the existence of electrostatic waves.
- 17:20 Influence of standing waves on the solution of the inverse problem of reconstructing parameters of a dielectric inclusion in a waveguide
- We develop and apply computer codes implementing the FDTD algorithm with perfectly matched layer (PML) absorbing boundary conditions for numerical solution of the nonstationary Maxwell equations. The aim of solving forward and inverse scattering problems is a determination of the dielectric media parameters of inclusions in a waveguide of rectangular cross-section using the transmission coefficient. Aposteriori estimate of the amplitude of higher-order evanescent waves is obtained and their influence on the choice of parameters of the numerical method is determined.

Conveners: Ludger Klinkenbusch and Giuliano Manara

Room: BChairs: Ludger Klinkenbusch, Giuliano Manara

- 08:40 Light Scattering into Two Fixed Angles vs. Angle-Resolved Measurements for Characterization of Single Submicron Particles
- Single particle identification and characterization based on scatter measurements is widely used in numerous biomedical applications. This scatter-based characterization approach implies a solution of the parametric inverse light-scattering (ILS) problem. The need for high-speed analysis limits the amount of collected scatter information and motivates maximum simplification of optical model of analyzed particles. We analyzed the capabilities and limitations of two existing approaches, based on measurement of either two scattering signals or angle-resolved patterns, applied to characterize single submicron particles. The standard flow cytometric approach is based on light scattering measurements into two fixed angles, forward and side scattering, which are further fitted by the Mie theory. We showed that corresponding ILS problem may have multiple solutions, and the procedure results in uncontrollable errors if the particle is not spherical. By contrast, angle-resolved scattering measurements have much larger information content at a cost of reduced analysis speed. This approach coupled with rigorous solution of ILS problem is shown to provide accurate identification and characterization of biological particles, including nonspherical ones.
- 09:00 Recent Developments on the Iterative Physical Optics for the Analysis of Electrically Large Scatterers (Invited)
- The most recent developments of an efficient Iterative Physical Optics (IPO) algorithm for analyzing the electromagnetic scattering of complex and electrically large scenarios are presented. The algorithm predicts multiple interactions between the objects comprised in the scenarios under the Physical Optics (PO) approximation. Various techniques for accelerating and parallelizing the algorithm have been used, thus obtaining an efficient tool that can be used in to realize a novel class of high-frequency solvers.
- 09:20 On Sum Rules for Scattering in Circular Polarization (Invited)
- Classical sum rules, that connect the dynamic scattering properties at all frequencies to the static polarizability, can be shown to break down when applied to circular polarization. This has previously been explained in terms of a breach of symmetry with respect to positive and negative frequencies. In this paper, we show an alternative explanation where circular polarization is introduced by using a branch cut in the complex plane. A numerical example for a spherical helical scatterer illustrates the results.
- 09:40 Transition Function for Describing Metasurface Dispersion (Invited)
- In this paper, analytical modeling of dominant mode dispersion is proposed for the rapid and accurate analysis of impenetrable Metasurfaces (MTSs). The model is based on an analytical representation of the homogenized MTS impedance in terms of a transition function, depending on one parameter only, which is an equivalent quasi-static capacitance. This approach enables one to accurately capture the physics of the surface-wave (SW) supported by the MTS, and provides accurate results up to the Floquet-Bloch region of the dispersion diagram.
- 10:00 Diffraction by Thick and Loaded Slit -E-polarization Case- (Invited)
- High frequency asymptotic method has been applied to formulate E-polarized plane wave diffraction by a thick and loaded slit. Internal slit region is considered as a waveguide and excitations of the waveguide modes are given by ray-mode conversion method from the multiply bouncing diffracted fields. Comparison with the results by the other method reveals the validity and the effectiveness of our formulation.
- 10:20 Tailoring Dielectric Resonator Geometries for Directional Scattering, Huygens' Metasurfaces, and High Quality-Factor Fano Resonances
- Metamaterial dielectric resonators represent a promising path toward low-loss metamaterials at optical frequencies. In this paper we utilize perturbations of high symmetry resonator geometries, such as cubes, either to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering and Huygens' metasurfaces, or to induce couplings between the otherwise orthogonal resonator modes to achieve high-quality factor Fano resonances. Our results are fully scalable across any frequency bands where high-permittivity dielectric materials are available, including microwave, THz, and infrared frequencies.

Conveners: Gregor Tanner and Gabriele Gradoni

Room: CChairs: Gregor Tanner, Gabriele Gradoni

- 08:40 Random Matrix Theory of Resonances: an Overview (Invited)
- Scattering of electromagnetic waves in billiard-like systems has become a standard experimental tool of studying properties associated with Quantum Chaos. Random Matrix Theory (RMT) describing statistics of eigenfrequencies and associated eigenfunctions remains one of the pillars of theoretical understanding of quantum chaotic systems. In a scattering system coupling to continuum via antennae converts discrete energy levels into decaying resonance states associated with poles of the scattering matrix in the complex energy plane. Understanding statistics of these poles, as well as associated residues related to non-orthogonal eigenfunctions within RMT approach is still possible, though much more challenging task.
- 09:00 Exact Results for Chaotic Scattering and Applications to Microwave Experiments (Invited)
- Scattering theory as developed in nuclear physics and related theories from other fields find numerous applications in a variety of different wave systems, ranging from the quantum to the classical scale. When the system is chaotic or in another sense sufficiently complex, statistical methods involving random matrices can be used to calculate precise predictions of distributions and correlation functions. Closely related approaches are now routinely used in wireless communication. I report our solution of a long--standing problem which is of particular interest for data comparison, namely the distribution of the off--diagonal scattering matrix elements. I demonstrate that our results fully describe recent microwave experiments.
- 09:20 Universality and Short-Wavelength Approximations for Chaotic Wave Scattering (Invited)
- We give an overview of wave scattering in open cavities in which the ray dynamics is chaotic. In the limit of short wavelengths certain properties emerge that are universal and do not depend on the details of the cavity. These universal features are described by random matrix theory. We discuss in particular results that characterize the transmission probabilities and transmission times of waves through the cavity. Short-wavelength approximations that use statistical properties of long rays are able to explain this universality.
- 09:40 A Phase-Space Approach for Propagating Field-Field Correlation Functions Near Stochastic Sources
- Radiation from complex and inherently random but correlated wave sources can be modelled by exploiting the connection between correlation functions and the Wigner function. Wave propagation can then be directly linked to the evolution of ray densities in phase space. We discuss here in particular the role of evanescent waves in the near-field of non-paraxial sources. We give explicit expressions for the growth rate of the correlation length as function of the distance from the source.
- 10:00 Transfer operator approach for cavities with apertures
- We describe a representation of the boundary integral equations for wave propagation in enclosures which leads to a direct description of transport and dynamical characteristics of the problem. The formalism is extended to account for arbitrary and possibly statistical sources driving a polygonal cavity problem and to account for apertures. In this approach, the boundary integral equations are encoded within a shift operator which propagates waves leaving the boundary until they return to the boundary as an incoming wave. The response of the system to non-deterministic, statistical sources characterized by correlation functions can be treated, providing a direct path to ray-tracing approaches through the Wigner function. The high frequency limit is retrieved semi-classically and provides a simple ray tracing scheme transporting densities of rays as an averaged response. Interference effects due to transport along multiple paths can also be accounted for.
- 10:20 Semiclassical Modeling of Individual and Arrayed Nanoantennas in the Quantum Plasmonic Regime
- We put forward here design and semiclassical modeling of nonlinear and reconfigurable optical metasurfaces formed by arrayed nanoantennas with nano/subnano-scale feed-gaps, where the photon-assisted tunneling results in a set of linear/nonlinear quantum conductivities. We show that optical nonlinearities sourced from higher-order quantum conductivities may be boosted by the plasmonic resonance and the large local field enhancement in the load region of nanoantenna. We discuss two exciting applications of the proposed nanoantenna-based devices: efficient frequency multiplication at the nanoscale and dynamic resistive switching for holographic imaging.

Room: D

Chairs: Anja K. Skrivervik, Anu Lehtovuori

- 08:40 Effect of Shape Deformation of a Patch Antenna on Its Characteristic Modes
- This paper studies how deforming the shape of a patch antenna affects its characteristic modes by applying the characteristic modes theory to analyze EM fields in antenna designs. The resonant frequencies of the lowest modes are in special focus in order to excite several modes in as small a space as possible.
- 09:00 Density tapering for antenna arrays based on a coordinate transform
- A differential equation is established to transform an array with constant average density into an array with prescribed density. It is shown that this allows good control over the first few sidelobes. This is especially true when combined with a limited amplitude weighting that compensates for local density variations, with limited effect on the array sensitivity.
- 09:20 Linear Antenna Synthesis with Maximum Directivity using Improved Fruit Fly Optimization Algorithm
- Linear antenna array synthesis with maximum directivity using an improved fruit fly optimization algorithm with adaptive fruit fly swarm population size, namely IMFOA, is presented in this paper. The IMFOA is a recently explored, highperformance algorithm, and suitable for solving the optimization problems. To show the versatility of the presented method, the objective of antenna design is to achieve maximum directivity for linear antenna array by controlling amplitude and spacing parameters of the array antenna. A design example is presented that illustrate the use of the IMFOA, and the optimization goal in example is accurately provided and easily achieved. The result of the IMFOA is validated by comparing with results obtained using the MFOA method, and GA/Fminsearch method. Finally, the IMFOA method is efficient and accurate for electromagnetic problems of the linear antenna array in free space.
- 09:40 Propagation in Cellular Networks
- Received signal level measurements are frequently used to check the performance and the Quality Of Service (QOS) inside the coverage area in cellular networks. These expensive time consuming measurements are carried out using actual drive tests to assess the coverage area of a base station for a given cell and thus evaluate the QOS. In a drive test measurement system, a receiving antenna is placed on top of a vehicle and the vehicle is then driven along radial and circular lines around the base station to measure the received power and thus assess the QOS. These drive test measurements are also used to tune the empirical models in the radio planning tools which have to be carried out for various types of environments. This model tuning is a lengthy procedure. In this paper, it is shown that an electromagnetic macro modeling of the environment can provide simulation results comparable to the data as one would obtain in an actual drive test measurement for a cellular environment. The input parameters for the electromagnetic macro model can be generated using only the physical parameters of the environment like the height of the transmitting and receiving antennas over the ground, their tilts towards the ground, and the electrical parameters of the ground. Such analysis can provide realistic plots for the received power versus separation distance between the receiving and the transmitting base station antennas. The novelty of the electromagnetic analysis technique proposed in this paper lies in its ability to match the macro model-based simulation results and the drive test measurements without any statistical or empirical curve fitting or an adhoc choice of a reference distance. A method of moments-based integral equation solver code has been used to simulate the effects of the macro parameters of the environment on the propagation path loss of the signals emanating from a base station antenna. This code is based on Sommerfeld Green's function to treat the imperfectly conducting planar ground.
- 10:00 Time Domain Reciprocity and the Transfer Response of Coupled Antennas
- A direct time domain derivation of the transfer response of two parallel dipole antennas in close proximity is performed by using two types of reciprocity theorems: convolution type and correlation type. The two formulations differ in the temporal mutual action between the time dependent quantities involved in the reciprocity process. Using an approximate expression for the dipole's current gives a convenient expression for the transfer response that can further be used for the analysis of the roles of different delayed wave-field contributions and causality.
- 10:20 Near-Field Focused Radiation by Two Edge-Coupled Microstrip Antenna Arrays
- This paper presents the radiation characteristics of two planar microstrip arrays which are mechanically arranged so that they share one of their border. For both the planar arrays, the phase profile of array excitation has been chosen to get a focused radiated field at a point in the antenna near-field region. This structure is suggested to enhance the field strength and reduce the spot size, with respect to a single planar focused array. A numerical parametric study over some geometrical parameters is given, to show the focusing performance of the proposed configuration.

Chair: Seppo Järvenpää

- Power Effect of Polar Summer Mesosphere Dusty Plasma on Space Microwave Energy Transmission
- Polar summer mesopause region belong to dusty plasma, the impact of dusty plasma on the electromagnetic signals have been verified by lots of experiments. If the system of space microwave energy transmission will be used in high latitudes of both hemispheres in the future, we need to pay more attention on dusty plasma in polar mesosphere. In the paper we will discuss signal effect of polar summer mesosphere dusty plasma on space microwave energy transmission.
- Electromagnetic Characterization of a Metasurface-enabled Frequency Reconfigurable Antenna
- A scattering-parameter-based method to determine electromagnetic properties of a metasurface-enabled frequency reconfigurable antenna is presented in this paper. In order to overcome the challenge of modeling the thin metasurface, we treat it together with the antenna superstrate as a slab, whose effective thickness is then numerically settled. Anisotropy is further included in the effective medium model, which improves the flexibility and the accuracy of the characterization process. The method is validated by numerical experiments.
- Antenna Array De-Embedding and Reciprocity Constraint
- The multistatic response matrix, obtained typically in the microwave imaging experiments, not only reflects the properties of the specific target, but also depends on both the geometry of the Tx/Rx arrays and the radiation patterns of the antenna units. An effective antenna de-embedding algorithm is proposed, which incorporates the reciprocity constraint. The latter is shown to essentially improve the performance of target recovery from undersampled and noisy data.
- Radiation Pattern of Rectangular Patch Antenna with Curved Surface
- In this paper, we analyze radiation pattern of a rectangular patch antenna with curved surface by means of mathematical approach. Aperture size of the curved patch is equivalently reduced in comparison with a flat surface patch antenna, so that its antenna gain slightly decreases and beam-width broadens. Because electrical size of patch is generally small, it is adequate to employ numerical calculation approach such as Method of Moment. However we try to employ analytical approach, Aperture Field Method, to the curved rectangular patch element. The radiation pattern is found to be expressed by Fresnel integral since phase distribution of main two slots can be approximated to quadratic shape.
- Electromagnetic mode profile shaping in waveguides
- Electromagnetic mode profile shaping, would be a very useful technique, with applications including in accelerator science and data transmission. Two methods are proposed, one using a negative permittivity, the other using a wire medium.
- Compact Microstrip Feedings with an Elevated Ground Plane for Thick Folded SIW
- Folded substrate integrated waveguide (FSIW) has been proposed for further size reduction, while keeping the advantages of traditional SIW. FSIW-based horn antennas are very promising in millimeter wave applications. To improve the bandwidth and efficiency of such antennas, a thick substrate is preferred but the microstrip feeding line becomes unacceptly wide to obtain a reasonable impedance. This paper introduces compact microstrip feeding lines with an elevated ground plane for thick FSIW. Arbitrary characteristic impedance can be achieved without increasing the width of the feeding line, which will be very useful for the integration with other millimeter circuit components.
- A Novel UWB antenna for Vehicle-to-Infrastructure Automotive Applications
- A novel ultra wideband antenna is here proposed for Vehicle to Infrastructure (V2I) communication systems. Two Vivaldi antennas are arranged in a back-to-back configuration (array of two Vivaldi antennas) to radiate both in front and rear car driving direction. By feeding the antennas with out-of-phase currents, the field radiation in the transversal direction is attenuated, so limiting the multipath effect due to buildings along the road. Since the antenna is mounted on a metallic car roof, its height has been split in half according to the Image Theorem.
- Electromagnetic Field Theory as System Theory
- This paper presents a transformation of Maxwell's equations for general nonlinear material operators into a system state equation of an equivalent nonlinear distributed parameter system. The proposed formulation has a fair amount of practical and didactic advantages, with regard to modeling hysteresis and memory effects, understanding causality, control and stability of electromagnetic fields, formulating multiphysics models, as well as computing analytic solutions or constructing numerical solution algorithms.
- On the Issue of Simulating Very Large Endfire Arrays with Complex Antenna Geometries
- This paper discusses some of the main issues of efficient analysis of electrically very large endfire arrays, and further proposes approaches for developing flexible simulation tools for this particular purpose. Some initial results supporting the endfire array design issue are presented, as well as some preliminary examples of implemented compression- and acceleration methods.
- Development of a Rain Attenuation Model for Terrestrial Links Using a Physically-Based Approach
- This contribution investigates the path reduction factor (PF) on terrestrial links, a typical element of rain attenuation prediction models, introduced to take into due account the spatial inhomogeneity of rainfall. A large number of PF values are calculated by simulating the interaction of a hypothetical terrestrial link with a set of realistic rain fields synthesized by MultiEXCELL. The dependence of PF on different quantities such as the path length, the operational frequency, and the rain rate measured at the transmitter, is addressed. Based on that, the contribution also illustrates the preliminary modeling steps oriented to the development of a new analytical methodology for the physically-based prediction of the rain attenuation affecting terrestrial links.
- A preliminary work on the discrimination of magnetic properties by means of TDR data
- In this contribution we deal with the problem of measuring both the dielectric permittivity and the magnetic permeability of a material with a TDR probe. Preliminary simulations based on the only the TEM propagation mode shows that it is possible to identify magnetic properties from measures of reflected field in time domain and measures of reflection coefficient in frequency domain.
- Tunable Leaky-Wave Antennas with RF MEMS
- RF MEMS switches are nowadays based on more and more mature technology and therefore have become components to introduce tunability into established devices. In this contribution it will be shown, how RF MEMS can be combined with conventional leaky-wave antennas. Either to enable an active beam steering and thus to reduce the number of phase shifters needed. Or to correct the beam squinting over frequency and so to create a broadband structure.
- Multiple Scattering by Dense Random Media: Volume-Element Extinction
- We consider multiple scattering of electromagnetic waves in dense discrete random media of particles. Here we focus on the exact computation of the coherent and incoherent scattered far fields for finite volume elements of spherical particles. We solve the scattering problem with the Superposition T-matrix method. We derive the incoherent extinction coefficient and, subsequently, the extinction mean-free-path length for volume elements with varying numbers of spherical particles as well as varying volume fraction of particles. In addition to confirming known results for incoherent scattering, we show new results, in particular, for the polarization effects in incoherent scattering.
- Dielectric Permittivity Dependence on Moisture Content
- In this paper, relative dielectric constant of magnolia and monstera leaves with respect to moisture content has been proposed at X-band. Leaf samples sandwiched with Plexiglas side holders are inserted within waveguide sections, and the dielectric constants are calculated from the complex transmission coefficient S21. It has been obtained that relative dielectric constant of magnolia and monstera leaves are decaying by relative moisture content as expected in this frequency band region, and relative dielectric constant of both of those leaves' samples doubles its value while moisture content doubles from 50% to%100. Two different relative dielectric constant calculation approaches (methods) have been selected, it has been observed that both methods predict very close results.
- On zero-reflection and zero-transmission of a stratified lossy medium
- In this paper a method to analyze the zero-reflection and zero-transmission conditions through a stratified lossy medium, is presented. The interaction of the electromagnetic radiation with the stratified material is taken into account by means of the transfer-matrix approach. The complex plane wave propagation vectors are represented with the complex angle formulation. In order to obtain these zero conditions an adaptive method has been adopted. A numerical code has been implemented to compute the field all-over the space. Some numerical applications, in order to obtain an electric matching layer for a large range of angles, are presented. This approach can be easily extended to an arbitrary number of layers to realize an intermediate layer with exotic properties.
- Amplitude and Slope Diffraction Coefficients for S-UTD-CH Model
- Diffraction mechanism is vital to predict the field strength and calculate the coverage in urban, rural and indoor. Diffraction occurs on the sharp surfaces like rooftop, edge, corner, and vertex. S-UTD-CH model computes three type of electromagnetic wave incidence such as direct, reflected and diffracted waves, respectively. In the case of close obstacle height, diffraction mechanism is dominant. In order to calculate the diffracted field amplitude and slope diffraction coefficient and first and second derivative of these have to derive correctly. In this paper, derivations will be made knife edge and wedge structures. Analysis about amplitude and diffraction coefficient will be made.
- Plane-wave Reflection from the Interface of a Novel Uniaxial Medium with Extreme Parameters
- In this paper, we present a reflection analysis of a plane wave incident on an interface of a novel electric-magnetic uniaxially anisotropic medium characterized by extreme constitutive parameters: very large transverse and very small longitudinal components of permittivity and permeability tensors. The novelty of the medium is specified by choosing the particular material properties. Such materials have been proposed for the realization of a perfectly matched layer and DB boundary conditions. DB boundary conditions require cancellation of normal components of electric and magnetic fluxes on the boundary surface. We study the reflection from the interface of the uniaxial medium by assuming that the optic axis of the material is arbitrarily oriented. We discuss the effect of the direction of the optic axis on the reflection characteristics and emphasize on its importance for the realization of electromagnetic absorbers. The behavior of the medium is also examined by varying the direction of the plane of incidence with respect to the plane of the optic axis. From numerical results we note that the medium shows very interesting properties of behaving as a perfect reflector, a perfect transmitter and a polarization inverter depending upon the direction of the optic axis and the plane of incidence.
- Plasmonic Modes on Rounded Hexahedral and Octahedral Nano-Antennas
- In this paper, the resonant spectrum of plasmonic, Drude-like, silver nano-antennas is presented. The central focus is the study of the radiation pattern of shapes, such as rounded cornered hexahedra and octahedra, under a full electrodynamic surface integral equation numerical scheme. Several aspects regarding their dipole, quadrupole, and higher order far-field distribution are revealed, giving special emphasis in their qualitative characteristics. Aspects of their resonant behaviour, such as quadrupole mode "Huygens" nano-antennas or peculiarities related with their far field planes are further discussed, expanding our understanding on single plasmonic nano-antennas and their emerging functionalities.
- A Dual-Band Conformal Metamaterial Absorber for Curved Surface
- In this paper, an ultra-thin dual-band conformal metamaterial absorber has been presented for curved surface applications. The proposed structure consists of a periodic array of two concentric rings printed on a grounded dielectric substrate. The numerical simulation shows that two discrete reflection dips occur at 7.22 GHz (C-band) and 14.55 GHz (Ku-band) with reflectivities of -17.55 dB and -12.80 dB, respectively. Furthermore, the proposed structure is polarization-insensitive and wide angularly stable (upto 45 degree) for both TE and TM polarizations. Unlike conventional planar absorbers, the design is made of ultra-thin substrate (lambda/138 for lower frequency) and therefore can be used as absorber coating for planar as well as curved surfaces. Finally, a prototype has been fabricated and measured in anechoic chamber, which shows good agreement between the experimental and simulated responses.
- Degrees of Freedom of the Field and Maximum Directivity
- This contribution discusses the relationship between the number of degrees of freedom (DoF) and the maximum directivity for an arbitrary set of sources enclosed by a given spherical surface. In particular, it is shown that the number of DoF is equal to twice the maximum directivity. This provides a directivity limitation for arbitrarily sized antennas, thus, extending the validity of the known formulas for electrically large and electrically small antennas. This contribution discusses the relationship between the number of degrees of freedom (DoF) and the maximum directivity for an arbitrary set of sources enclosed by a given spherical surface. In particular, it is shown that the number of DoF is equal to twice the maximum directivity. This provides a directivity limitation for arbitrarily sized antennas, thus, extending the validity of the known formulas for electrically large and electrically small antennas.
- Single-sensor Imager for Very-High-Resolution Microwave Imaging
- This work presents a concept of single-sensor imager for very-high-resolution microwave imaging in combination with spatial-temporal lens and sparse reconstruction, which is verified by theoretical analysis and experiments. It is expected that such single-sensor imager also can find its valuable application for other imaging fields, using more specialized spatial-temporal lens and more efficient sparse reconstruction solver.
- Transmission-Line Modeling of Shielding Effectiveness of Multiple Shielded Cables with Arbitrary Terminations
- Cable shielding to protect against coupling of electromagnetic radiation into a component or circuit, particularly over large frequency bands, is at times a challenging task. It is general understanding that increasing the number of shields of a cable will improve the shielding performance. However, there are situations in which a cable with multiple shields may perform similar to or worse than a cable with a single shield, and this analysis has seldom been discussed in the literature. We intend to shed more light onto this topic in this paper.
- An Approach to Estimation of Solutions to Inverse Problems of Electromagnetics
- In this paper an approach is proposed which is based on a method of regularization for estimating the solution of inverse problems of electromagnetics with noisy measurements. The constraints on the solution of the inverse problem based on physical assumptions are taken into consideration. The solution is reduced to a nonlinear system with the given interval-type inaccuracy of the right-hand side. The developed approach enables one to take into account inaccuracy of the operator of the inverse problem. The method of the special mathematical model selection is described which improves the accuracy of estimations.

Computational Electromagnetics — Past, Present, and The Future

Jin-Fa Lee

Room: BChair: Giuliano Manara

- 13:40 Computational Electromagnetics — Past, Present, and The Future (Plenary)

Conveners: Cristina Ponti and Andrea Randazzo

Room: BChairs: Cristina Ponti, Andrea Randazzo

- 14:40 Analytical investigations of ground modifications assisting the detection of a buried object (Invited)
- A ground-penetrating radar (GPR) antenna excites a perfectly electric conducting inclusion buried inside the ground. The scattering problem is solved semi-analytically via integral equation techniques. The permittivity and thickness of a superstrate deposited atop the ground are determined such that the detectability of the inclusion is significantly increased. Results from numerical simulations are presented exhibiting the effectiveness of the approach. Emphasis is given on the effects that the shape of the buried inclusion has on the scattered field.
- 15:00 A first numerical assessment of the reliability of finite element simulators for time-harmonic electromagnetic problems involving rotating axisymmetric objects (Invited)
- In this work we show some results computed by the finite element method for time-harmonic electromagnetic problems involving rotating spheres. They are compared with the data provided by a semi-analytical technique. The comparisons show the reliability of the numerical method. In the presence of non-canonical rotating axisymmetric objects no comparison is possible but the reliability of finite element simulators seems to be independent of the shapes of the rotating bodies.
- 15:20 Frequency and Time Domain UTD Vertex Diffraction: a Heuristic solution and a step toward the exact one
- The diffraction by vertexes or corners is important in practical engineering applications when it is necessary to characterize the scattering of objects with arbitrary shapes and finite dimensions. In this paper we discuss some of the existing Uniform theory of diffraction (UTD) solutions present in the literature. We will focus our attention on frequency domain heuristic solutions, which is then also extended in the time domain. Finally, we will discuss about the possibility of developing novel hybrid numerical-asymptotic solutions which can improve the existing ones.

Conveners: Gregor Tanner and Gabriele Gradoni

Room: CChairs: Gregor Tanner, Gabriele Gradoni

- 14:40 Uncertainty Quantification of Propagation in Evaporation Ducting
- The Fourier split-step method is used for solving parabolic equations in, for example, computational electromagnetics. In this paper we develop a spectral based Fourier split-step method that will take a limited degree of information with regard to the refractive index of the atmosphere into account.
- 15:00 Inhomogeneous Wave Penetration in Lossy Media
- The penetration properties of inhomogeneous waves are illustrated. A theoretical approach is presented and a leaky-wave antenna design is proposed in order to verify the theoretical implications. Practical aspects related to the excitation of leaky waves able to give rise to deep penetration effects in lossy media are discussed and the possible implementation issues are commented.
- 15:20 Comparison of Ray Traced Based Models with Physical Optic Model
- Electromagnetic wave propagation in free space is an excessively simplified situation. Hence, the vital question is how an electromagnetic wave propagates in ambient including obstructions like mountains, trees, hills or buildings. These obstructions reflect, diffract and scatter the electromagnetic waves. UTD and S-UTD models are ray-tracing-based electromagnetic wave propagation models and are shortly explained in this paper. In addition, exhaustive information is supplied about the improved slope UTD model, which is called the S-UTD-CH model. Electromagnetic wave propagation models, which are UTD, S-UTD, S-UTD-CH and PO, are compared with regard to prediction accuracy and computation time among themselves. Widespread simulation results are provided to compare the models in terms of prediction accuracy and computation time. Moreover, the S-UTD-CH model is considered an optimum model in terms of its accuracy and computation time. Furthermore, how the transmitter antenna height, the distance between buildings and the operating frequency affects the relative path loss at the receiver are analyzed.

Room: D

Chair: Mario Silveirinha

- 14:40 Effective Parameter Calculation of 3D Bianisotropic Scatterer Arrays through Extracted Polarizabilities
- In this paper, an efficient technique for computing the bulk parameters of infinite, normally-illuminated 3D arrays is developed. Initially, the dispersion equation of the array is derived and, then, the complex wavenumber for the TEM case is obtained through a rigorous algorithm. The retrieved polarizabilities of a single scatterer and the wavenumber are, finally, incorporated in first-principles homogenization formulas to evaluate the effective parameters. The proposed method is applied to popular bianisotropic scatterers and the validity of the results is successfully certified via numerical simulations.
- 15:00 Left handedness and asymmetric excitation in linear arrays of isotropic electric-magnetic particles
- We study the properties of wave propagation in linear chains of particles with both electric and magnetic response. In the case of transverse modes, and in contrast to the purely electric case, there are dispersion branches which lack light-line modes. Using Z-Transform the variety of modal properties are revealed and the inherent left-handedness and excitation asymmetry in the chain modes is demonstrated. Left handed modes are observed also for positive polarizability particles.
- 15:20 Analysis of Waveguide Discontinuities with Lateral and Transverse Perfect Magnetic Wall Boundary Conditions
- This contribution presents the analysis of waveguide problems involving general boundary conditions of perfect magnetic wall. This type of boundary condition, when the waveguide device under analysis has physical symmetry, is used very commonly to speed up the computation time in general waveguide solvers by exploiting the symmetries of the excitation. This contribution is focused on extending its use in general problems having this type of boundary condition in the lateral and transverse walls, applying the mode-matching method. The formulation will be applied to classical waveguide devices surrounded by perfect magnetic walls, but also to simulate radiating problems. The simulation results will be compared with those obtained by other numerical techniques (based on different solvers) to test the validity of the presented formulation.

Conveners: Matteo Pastorino and Lianlin Li

Room: BChairs: Matteo Pastorino, Lianlin Li

- 16:00 Hard Thresholding Based Compressed Sensing Approach for Thermoacoustic Tomography
- In this paper we present a reconstruction method based on compressed sensing for thermoacoustic tomography. The proposed method combines hard thresholding algorithm with conjugate gradient method to solve the inverse source problem of thermoacoustic tomography. Within the compressed sensing approach, the method is applied to thermoacoustic tomography. Numerical results for two different scenarios verify that the proposed method improves the image reconstruction quality with under-sampled data.
- 16:20 Real GPR Signal Processing for Target Recognition with Circular Array Antennas
- In this paper, 3D imaging of forward-looking Ground Penetrating Radar (GPR) data acquired by rotating antennas have been done. The data acquisition procedure mimics data collection of the Tunnel Boring Machine (TBM). Real GPR data for a Karst scenario were analyzed, preprocessed and finally imaged with back-projection method. Results show that objects buried in the subsurface of the ground can be successfully imaged using rotating antennas, which is a solid foundation for further development of the GPR system on TBM.
- 16:40 Back-Projected Cortical Potential Imaging for Monitoring and Stimulation Tools
- In this work, a new method for cortical potential imaging (CPI) is presented. The potential distribution measured on the scalp during standard EEG procedure is back-projected to the cortex surface using an electroquasistatic mechanism. The proposed method combines the information from MRI derived realistic head conductivity model with approximated boundary conditions (surface Laplacian) of the cortical normal currents, together with the finite element method (FEM). The back-projection CPI (BP-CPI) which gives a simple, fast, high-resolution and accurate CPI, solved in only one iteration. The BP-CPI was designed for easy integration with monitoring and stimulation tools for better understanding the underlying cortical activity. The analysis is backed by simulative validation results.
- 17:00 Design, Fabrication and Measurement of Polarization Insensitive Metamaterial Broadband Absorber for Radar Invisibility Applications
- Metamaterial based absorbers have great potential for radar invisibility applications. With perfect and broadband absorption, they can be used against radars as reducing radar cross section. Radar cross section (RCS) of relevant targets representing the visibility in radar can be reduced by coating target with metamaterial absorbers. Therefore, metamaterial based electromagnetic wave absorbers have become one of the major research areas in recent years. In this paper; design, simulation, optimization and measurement of a polarization insensitive broadband metamaterial absorber are presented in microwave frequency band. It is observed that the experimental results are in good agreement with the simulations. Measurement bandwidth for an absorption level of 90 % is 2.5 GHz in the frequency range. Radar cross section reduction of the proposed metamaterial absorber compared with a fully metallic plate is also investigated numerically and experimentally. 10 dB RCS reduction is achieved over the range of 9-11.5 GHz.

Conveners: Matti Lassas and Petri Ola

Room: CChairs: Matti Lassas, Petri Ola

- 16:00 Boundary shape reconstructions in a coaxial waveguide using Bessel functions
- This paper investigates boundary shape reconstructions in coaxial waveguides using microwave scattering. Electromagnetic field perturbation theory together with inverse problem theory is used to reconstruct two-dimensional small boundary deformations on the inner boundary of a coaxial waveguide. Due to the first-order perturbation theory employed, the scattering parameters of the waveguide have linear dependencies on the continuous deformation function. Thus, the corresponding inverse problem can be linearized, and direct inversion can be employed to obtain the shape parameters. Tikhonov regularization is used to regularize the resulting ill-conditioned linear system. Finally, reconstruction results are presented for a few examples of two-dimensional localized shape deformations of coaxial waveguide boundaries, being in agreement with the known actual shapes.
- 16:20 Estimation of Complex Valued Permeability of Cable Armour Steel
- This paper presents a model based technique to estimate the complex valued permeability of cable armour steel. An efficient analytical model is derived for the linearized mutual impedance of a transformer coil built on a core of magnetic armour steel. A numerical residue calculation is used to solve the related inverse problem based on impedance data. The analytical model is validated using commercial finite element (FEM) software to establish that edge effects can be neglected. The numerical residue calculation is investigated by studying its convergence based on a simple rectangular quadrature rule in comparison to the composite Simpson's rule. When there are no measurement errors, both methods converge with an unexpected high order (superconvergence). However, in practice the estimation performance will be governed by measurement and model errors. Assuming that there are Gaussian measurement errors, the present performance of the estimation technique is quantified and investigated by means of the Cramer-Rao lower bound. In future, the proposed method will be useful as an input to general calculations of power losses in three-phase power cables.
- 16:40 On the Spectrum and Preconditioning of Electromagnetic Volume Integral Equations (Invited)
- Spectral properties of current-based volume integral equation of electromagnetic scattering are investigated in the case of isotropic and bi-isotropic objects. Using Helmholtz decomposition the spectrum is derived separately for the solenoidal, irrotational, and harmonic subspaces. Based on this analysis, preconditioning strategies of the matrix equation are discussed.
- 17:00 Generation of inhomogeneous electromagnetic waves by a lossy prism
- The generation of inhomogeneous electromagnetic waves in free space is associated to the leaky-wave antennas. On the other hand, in the present paper, we show how an inhomogeneous wave can be also generated by the transmission of a homogeneous wave incident on a dissipative material with a spatial inhomogeneity. In fact, if we consider a dissipative material immersed in free space, with the first interface illuminated by a homogeneous wave, the spatial inhomogeneity gives to the wave different attenuations in the transverse direction; consequently the wave obtains an attenuation component tangential to the second interface, that imply the generation of an inhomogeneous wave in the free space. In particular, we consider a prism made of dissipative material illuminated by a horn tapered antenna. We present the phase and attenuation vectors' magnitudes, and the transmission angle of the inhomogeneous wave. The phase and attenuation vectors showing a strong dependence on the incident angle. Moreover, we found the optic path of the wave inside the prism during multiple reflections, in order to find the positions of the secondary lobs of the antenna. The possibility to generate inhomogeneous waves with strong attenuation finds applications for the deep penetration of electromagnetic waves in lossy materials.

Conveners: Hendrik Rogier, John Volakis, Sam Agneessens and Asimina Kiourti

Room: DChairs: Hendrik Rogier, John L. Volakis

- 16:00 A Foldable Textile Patch for Modular Snap-On-Button-Based Wearable Antennas (Invited)
- A concept of modular textile antenna design with commercial snap-on buttons has been proposed recently for wearable applications. The concept was shown to provide passive system reconfigurabilities in regard to resonance frequency and polarization without modifications to the feeding structure. As an extension of this work, a foldable patch module is presented in this paper for the antenna concept, demonstrating further passive discrete resonance frequency modularity at 8, 9 and 10 GHz. Through a simple folding of the textile radiating element at predetermined lengths denoted by position markers, particular resonance frequencies can be manually interchanged. Prototype-based experimental characterization shows a good agreement with simulations, which indicates that the foldable module performs as expected. This design emphasizes that the reported modular antenna design promotes a practical, lowmanufacture-cost, low-maintenance-cost, passive and versatile solution to reconfigure system characteristics for multi-functional wearable systems.
- 16:20 Flexible Millimetre-Wave Frequency Reconfigurable Antenna for Wearable Applications in 5G Networks (Invited)
- In order to keep pace with the growing research and development on millimetre-wave (MMW) antennas for the fifth generation (5G) networks, this paper integrates the frequency reconfigurability in a flexible antenna operating at MMW frequency spectrum. The proposed antenna is designed on liquid crystal polymer (LCP) substrate which is currently well recognised for its distinguishing performance at high frequencies. Antenna geometry consists of a radiating patch like a shape of tuning fork and two stubs which can be made part of radiating element by means of two switches. The proposed antenna offers a frequency reconfiguration over an operating range of 20.7-36 GHz by four different switch configurations. Surface mount PIN diodes have been assembled on LCP substrate as a switch. Inkjet printing has also been suggested for fabrication. The proposed antenna is well suited for wearable communication systems and body-centric applications for future 5G networks because of its notable features of conformity, light-weight, high-efficiency, and frequency reconfigurability.
- 16:40 A Theoretical Analysis to Reduce the Human Body Effect on Wearable PIFAs Performance (Invited)
- The robustness of wearable UHF-band grounded antennas with respect to body-coupling effects is addressed through numerical investigations. Main goal is gaining physical insights on the relationship between the grounded antenna performance and the distribution of the electric and magnetic energy densities in the antenna near-field region close to the ground plane border. Two UHF Planar Inverted-F Antennas suggested in the open scientific literature for the implementation of Radio Frequency Identification (RFID) transponders and off-body communication systems, have here been considered as examples for the investigation. A criterion for choosing a proper shape of the antenna ground plane is specified, which can increase the antenna robustness with respect to the body-coupling effects, but with a minimal impact on the antenna size.
- 17:00 Minimum of Two-Port Voltage and Power Gain under Varying Terminations: Semi-Analytical Method and Application to Biotelemetry Systems (Invited)
- We analyze the structure of the level sets of voltage gain and transducer power gain in two-port systems and based on the findings, present a semi-analytical method for finding the minimum values of these quantities as the port terminations vary in bounded rectangles in the complex plane. This provides a numerically efficient way to assess the impact of variability in the port terminations to the system performance. As an example, we investigate the impact of imperfect impedance matching to the performance of a biotelemetry system composed of magnetically coupled small loops.