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Numerical techniques for calculating electromagnetic fields within three-dimensional surfaces are computationally intensive. Therefore, this paper presents the application of a mode-matching technique developed for analyzing electromagnetic scattering from periodic comb surfaces illuminated by a plane wave. A set of linear equations has been developed to calculate mode coefficients of the field distribution for both E- and H-polarized incident waves. Analysis is performed for two cases where the comb thickness is either infinitely thin or of a finite thickness. The technique is shown to accurately predict both field intensities within the near-field of the periodic surface and far-field scattering patterns. Results are compared to those obtained using the finite integration techniques (FIT) implemented in CST Microwave Studio. Furthermore, numerical results are compared to measurements of an aluminum prototype. Additional far-field scattering measurements using a bi-static system provide additional confidence in CST simulations and the mode-matching methods presented here. [ABSTRACT FROM PUBLISHER]

The nonconformal domain decomposition methods (DDMs) of the hybrid finite element-boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA) are presented for computing large electromagnetic scattering/radiation problems. The numerical performance of different transmission conditions between finite element method (FEM) subdomains, and FEM and BI domains is studied in this paper. The Dirichlet transmission condition (DTC) employed at the interface between FEM and BI domains has faster convergence than the Robin-type transmission condition, and this finding is different from the conclusions for the FEM DDMs published in the literature. Furthermore, the cement-element (CE)-based dual-primal finite element tearing and interconnecting (FETI-DP) DDM has faster convergence than the Lagrange-multiplier-based FETI-DP method under the FE-BI system, and is also different from that under the system of the FEM with the absorbing boundary condition (FEM-ABC). It shows that the DDMs of FE-BI-MLFMA have some essential differences from those of FEM-ABC. The analysis of these numerical phenomena is presented in this paper. Further comparison between the DDMs of FE-BI-MLFMA and FEM-ABC demonstrates that the DDMs of FE-BI-MLMFA have essential advantages over those of FEM-ABC. Various numerical experiments confirm the accuracy, efficiency, and flexibility of the nonconformal DDM of FE-BI-MLFMA, which is the CE-based FETI-DP DDM with DTC connecting FEM and BI. [ABSTRACT FROM AUTHOR]

The well-known TE/TM decomposition of time-harmonic electromagnetic fields in uniaxial anisotropic media is generalized in terms of four-dimensional differential-form formalism by requiring that the field two-form satisfies an orthogonality condition with respect to two given bivectors. Conditions for the electromagnetic medium in which such a decomposition is possible are derived and found to define three subclasses of media. It is shown that the previously known classes of generalized Q-media and generalized P-media are particular cases of the proposed decomposable media (DCM) associated to a quadratic equation for the medium dyadic. As a novel solution, another class of special decomposable media (SDCM) is defined by a linear dyadic equation. The paper further discusses the properties of medium dyadics and plane-wave propagation in all the identified cases of DCM and SDCM. [ABSTRACT FROM PUBLISHER]

Electromagnetic scattering by penetrable bodies often is modelled by the Poggio-Miller-Chan-Harrington-Wu-Tsai (PMCHWT) integral equation. Unfortunately the spectrum of the operator involved in this equation is bounded neither from above or below. This implies that the equation suffers from dense discretization breakdown; that is, the condition numbers of the matrix resulting upon discretizing the equation rise with the mesh density. The electric field integral equation, often used to model scattering by perfect electrically conducting bodies, is susceptible to a similar breakdown phenomenon. Recently, this breakdown was cured by leveraging the Calderón identities. In this paper, a Calderón preconditioned PMCHWT integral equation is introduced. By constructing a Calderón identity for the PMCHWT operator, it is shown that the new equation does not suffer from dense discretization breakdown. A consistent discretization scheme involving both Rao-Wilton-Glisson and Buffa-Christiansen functions is introduced. This scheme amounts to the application of a multiplicative matrix preconditioner to the classical PMCHWT system, and therefore is compatible with existing boundary element codes and acceleration schemes. The efficiency and accuracy of the algorithm are corroborated by numerical examples. [ABSTRACT FROM AUTHOR]

A new wideband circular high-impedance surface (HIS) is proposed. Two models are developed to analyze the reflection characteristics of the proposed HIS. It is also shown through simulations that a circular HIS as a ground plane for loop antennas is superior to a rectangular HIS ground plane. The circular HIS was fabricated and a loop antenna was placed above it. Measurements were then performed and their results were compared with simulations. An excellent agreement was indicated. [ABSTRACT FROM PUBLISHER]

Subgridding methods are often used to increase the efficiency of the wave propagation simulation with the Finite-Difference Time-Domain method. However, the majority of contemporary subgridding techniques have two important drawbacks: the difficulty in accommodating dispersive media and the inability for physical interfaces to cross the subgridding interface. This paper presents an extension of the frequency-dependent Huygens subgridding method from one dimension to three dimensions. Frequency dependency is implemented via the Auxiliary Differential Equation approach using the one-pole Debye relaxation model. Numerical experiments indicate that subgridding interfaces can be placed in various Debye media as well as across the physical interface . [ABSTRACT FROM PUBLISHER]

In this paper, the authors present a method to reconstruct measured antenna radiation patterns and their related time-varying aperture fields. The method is based on a model that accounts for the measurement scenario and the antenna radiation characteristics through its radiation centers. The inputs to the model are radiation pattern measurements over a certain bandwidth. Solving the model provides the number of radiation centers, the patterns coupled with each radiation center, and the time delay at which these patterns would be measured. With this information one can reconstruct the measured pattern and retrieve the time-varying aperture fields of the antenna. The latter also provides a diagnostic tool for complex radiating structures. The method and the model are validated with measurements performed in a compact range of two spaceborne antennas. [ABSTRACT FROM AUTHOR]

The electric and magnetic current volume integral equation formulation is developed for the electromagnetic scattering analysis of arbitrarily shaped 3-D bianisotropic objects. The eigenvalue spectrum of the operator is derived and analyzed in the case of bi-isotropic media. The effect of inhomogeneity and bianisotropy on the spectrum and convergence of iterative solutions is investigated numerically. [ABSTRACT FROM PUBLISHER]

A new discontinuous Galerkin time-domain (DGTD) method based on generalized sheet transition conditions (GSTCs) for analyzing the transient response of electromagnetic metasurfaces is presented. The discontinuities in electromagnetic fields around the vicinity of the metasurface are modeled by placing virtual edges on both sides of the metasurface. The GSTCs are incorporated in the updating equations of the standard DGTD algorithm by integrating the time-domain GSTCs formula with Galerkin’ s-weighted residual method. The DGTD-GSTC formulation can also simulate a bf piecewise linear approximation of a curved metasurfaces due to the unstructured mesh. This is the first time that DGTD is applied to the simulation of GSTCs. The implementation of this new method is verified by numerical cases. [ABSTRACT FROM AUTHOR]

A stochastic finite-difference time-domain (S-FDTD) algorithm is presented for electromagnetic-wave propagation in anisotropic magnetized plasma. This new algorithm efficiently calculates in a single simulation not only the mean electromagnetic field values, but also their variance as caused by the variability or uncertainty of the electron and ion content of the ionosphere. The structure of the ionosphere is often too variable and uncertain for electromagnetic-wave propagation problems to be solved using a deterministic formulation, particularly during space weather events. For these cases, the S-FDTD ionospheric plasma algorithm will serve as an important tool. For example, it could be used to determine the confidence level at which a communications or remote sensing or radar system will operate as expected under abnormal ionospheric conditions. [ABSTRACT FROM PUBLISHER]

A novel technique has been suggested for the analysis of a transient electromagnetic field generated by a pulsed line current that is located near a planar interface between two dielectric nonabsorbing and nondispersive media. As distinct from the Cagniard-de Hoop method, which is widely used for the study of transient fields both in electrodynamics and in the theory of acoustic and seismic waves, our approach is based on the transformation of the domain of integration in the integral expression for the field in the space of two complex variables. As a result, it will suffice to use the standard procedure of finding of roots of the algebraic equation rather than construct auxiliary Carniard's contours. A fresh type of the representation for the field has been derived in the form of an integral along a finite contour. The algorithm based on the representation of this kind may work as the most efficient tool for calculating fields in multilayered media. The method suggested allows extension to the case of arbitrary dipole sources. [ABSTRACT FROM AUTHOR]

To enable an efficient stochastic-based design optimization methodology for multiscale structures of electrical devices, circuits, and systems, we propose the infusion of stochastic modeling with the electromagnetic macromodel in the method of finite-difference time domain (FDTD). We enhance the computational efficiency of the stochastic macromodel by applying the model order reduction techniques to produce the stochastic reduced-order macromodel. In addition, we provide a methodology and algorithms for the efficient generation and application of the stochastic reduced-order macromodel in the FDTD grid. The proposed methodology quantifies the impact of uncertainty in the electromagnetic system response that is manifested as random material and structural variations, through modeling and simulation. We demonstrate the proposed methodology by applying it to the computation of the stochastic transient electromagnetic fields in a 3-D bandgap structure comprising a rectangular waveguide, which contains an array of dielectric posts that exhibit uncertainty. [ABSTRACT FROM PUBLISHER]

With the purpose of avoiding very fine mesh cells in the proximity of a thin wire, the modified telegrapher’s equations (MTEs) are employed to describe the thin wire voltage and current distributions, which consequently results in reduced number of unknowns and augmented Courant–Friedrichs–Lewy (CFL) number. As hyperbolic systems, both the MTEs and the Maxwell’s equations are solved by the discontinuous Galerkin time-domain (DGTD) method. In realistic situations, the thin wires could be either driven or loaded by circuit networks. The thin wire–circuit interface performs as a boundary condition for the thin wire solver, where the thin wire voltage and current used for the incoming flux evaluation involved in the DGTD-analyzed MTEs are not available. To obtain this voltage and current, an auxiliary current flowing through the thin wire–circuit interface is introduced at each interface. Corresponding auxiliary equations derived from the invariable property of characteristic variable for hyperbolic systems are developed and solved together with the circuit equations established by the modified nodal analysis (MNA) modality. Furthermore, in order to characterize the field and thin wire interactions, a weighted electric field and a volume current density are added into the MTEs and Maxwell–Ampere’s law equation, respectively. To validate the proposed algorithm, three representative examples are presented. [ABSTRACT FROM PUBLISHER]

A novel amplitude-only measurement method is proposed for phased array calibrations. The proposed method can determine a complex element field at every phase shift of a digital phase shifter in phased arrays. The method can be realized using higher order Fourier coefficients of one array-power response measured with the conventional rotating element electric field vector (REV) method. Simulations and experiments were carried out, including transmission errors from the phase shifters, which validated the proposed method. More accurate calibration and beam forming can be achieved by using the precise element fields at all phase shifts determined by the proposed method. [ABSTRACT FROM PUBLISHER]

Electromagnetic scattering by general bi-isotropic objects is calculated by using the time-domain integral equations which are incorporated with the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) formulations. By introducing a pair of equivalent electric and magnetic sources, electromagnetic fields inside a homogeneous bi-isotropic region can be represented by these sources over its boundary after applying fields splitting method. A series of coupled surface integral equations are obtained after imposing boundary conditions. These equations are then solved numerically using the method of moment (MoM) which involves separate spatial and temporal testing procedures. The Rao-Wilton-Glisson (RWG) functions are used as the spatial expansion and testing functions, and the weighted Laguerre functions are derived as the temporal basis and testing functions. Numerical results such as transient currents, far scattered fields, and normalized radar cross sections are presented and compared with analytical results as well as MoM-based frequency-domain analysis, and good agreements are observed. [ABSTRACT FROM PUBLISHER]

The simple analytical formula for the electromagnetic field radiated by a horizontal infinitely long wire over the planar surface of the earth coated with a dielectric layer is derived. It is concluded that the total field includes four modes: the direct wave, the ideal reflected wave or image wave, the lateral wave, and the trapped surface wave. In particular, both the trapped surface wave and the lateral wave are examined in detail. From analysis and computations, it is demonstrated the trapped surface wave, which is determined by the sum of residues of the poles, can be excited efficiently. When both the infinitely long wire and the observation point are on or near the planar surface, the trapped surface wave is dominant. [ABSTRACT FROM PUBLISHER]

More insight on the physics underlying the transmission through subwavelength hole arrays prism by comparing it with propagating hole arrays prism is provided. We show the critical role that the size of the holes plays in this electromagnetic propagation, changing the effective index of refraction from negative (backward wave) to positive values (forward wave) as the hole diameter increases. This causes negative refraction for the zeroth order emerging beam in the cut-off holes prism whereas positive refraction in the non-cut-off holes prism. Furthermore, we revisited from the perspective of superposition principle the explanation of these stacks based on the so-called building sub-units: horizontal rods and vertical wires. Our simple analysis reveals the drawbacks of this earlier interpretation, and reinforces the powerful model founded on a inverse transmission line. Experimental results (co- and cross-polar measurements) performed at the V-band of the millimeter-waves in the Fresnel zone are well supported by numerical analyses. As expected, higher order diffracted outgoing beams are recorded for the classical prism but not for the cut-off holes prism. [ABSTRACT FROM AUTHOR]

Analytic time-domain expressions are derived for the pulsed electromagnetic field radiated by a wide slot antenna with a dielectric layer in a two-dimensional model configuration. In any finite time window of observation, exact pulse shapes for the propagated, reflected and refracted wave constituents are constructed with the aid of the modified Cagniard method (the Cagniard-DeHoop method). Numerical results are presented for field pulse shapes at the dielectric/free-space interface, the pulse time widths of the excitation being chosen such that the separate arrivals from the two edges of the slot can be distinguished. Applications are found in any system whose operation is based on pulsed electromagnetic field transfer and where digital signals are detected and interpreted in dependence on their pulse shapes. [ABSTRACT FROM AUTHOR]

A new iterative procedure is presented that enables method of moment (MoM) solution of scattered field from electrically large and complex perfectly conducting bodies using significantly reduced number of unknown coefficients. In each iteration the body is excited by a plane wave and by the currents, which are obtained as an approximate solution in the previous iteration. The physical optics (PO) and modified PO techniques are used to determine the PO and the correctional PO currents, which are expressed in terms of original MoM basis functions and grouped into macro-basis functions (MBFs). Weighting coefficients of all MBFs are determined from the condition that mean square value of residuum of original MoM matrix equation is minimized. The iterative procedure finishes when the residuum decreases below the maximum allowed value. The accuracy and efficiency of the proposed method are illustrated on two examples: cube scatterer and airplane scatterer. Since the construction of MBFs by PO and modified PO techniques ensures fast convergence to the original MoM solution, the method is named PO driven MoM. [ABSTRACT FROM AUTHOR]

Plasma can be used to create antennas: its conductivity is given by free electrons resulting from gas ionization. This process is obtained with the application of an intense electromagnetic field to a glass tube filled with a low pressure gas. The pump signal needed for ionization and gas discharge parameters have to be carefully chosen in order to optimize plasma antenna design and realization; in particular discharge working conditions have to be defined to obtain the desired antenna properties in terms of efficiency and effective length. For this purpose a self-consistent numerical model of a surface wave driven plasma column has been developed. This tool helps to understand the physical aspects involved in the problem and allows a parametric investigation to be carried out. [ABSTRACT FROM AUTHOR]

We investigate the spatial and frequency characteristics of electromagnetic fields scattered by some object. Frequency functions that allow the expression of all elements of the object scatter matrix are introduced. The sampling theorems that are proved for the introduced functions make it possible to characterize the scatterer by a set of discrete parameters. The application of the proved theorems provides for the creation of a versatile scatterer discrete model that determines the dependence of scattered fields both on spatial coordinates and frequency. A random scatterer is considered and the conditions under which the discrete parameters are statistically independent normalized random variables are stated. The article presents the results of a random scatterer modeling. [ABSTRACT FROM AUTHOR]

The adaptive integral method (AIM) is combined with the higher order method of moments (MoM) to solve integral equations. The technique takes advantage of the low computational complexity and memory requirements of the AIM and the reduced number of unknowns and higher order convergence of higher order basis functions. The classical AIM is appropriately modified to allow larger discretization elements and, consequently, higher basis function expansion orders. Numerical examples based on the higher order hierarchical Legendre basis functions show the advantages of the proposed technique over the classical AIM based on low-order basis functions in terms of memory and computational time. [ABSTRACT FROM AUTHOR]

The electromagnetic field behind buildings is calculated by making us! of the equivalence principle in two-dimensional environments. We derive equivalent currents on the building walls and other boundaries. The electromagnetic field at a receiver behind the building is calculated from those currents. We also visualize the Poynting vector field strength behind the building, which makes clear how the field is reflected or diffracted around the top of the building. We compare our result with a knife-edge model and a ray-tracing model, and we confirm that the equivalence principle provides predictions of the fields accurately. The calculation method is applied to multiple buildings by using it consecutively to obtain the field behind the last building. [ABSTRACT FROM AUTHOR]

A method is presented that combines the low-frequency accuracy of tree-loop decomposition with higher order basis functions to achieve an electric field integral equation based method of moments that is accurate over a wide band of frequencies. In general, the use of higher order divergence-conforming bases introduces more solenoidal degrees of freedom than the standard Rao-Wilton-Glisson (zeroth-order) bases. These solenoidal degrees of freedom are counted and identified, and an efficient method to construct the required higher order loops is presented. Numerical results demonstrate that the technique allows the use of a single mesh to acquire scattering results over a wide band of frequencies using arbitrary order basis functions. [ABSTRACT FROM AUTHOR]

This communications describes an electromagnetic model of a radial line planar antenna consisting of a radial guide with one central probe and many peripheral probes arranged in concentric circles feeding an array of antenna elements such as patches or wire curls. The model takes into account interactions between the coupling probes while assuming isolation of radiating elements. Based on this model, computer programs are developed to determine equivalent circuit parameters of the feed network and the radiation pattern of the radial line planar antenna. Comparisons are made between the present model and the two-probe model developed earlier by other researchers. [ABSTRACT FROM AUTHOR]

Presents information on a study which deals with the application of an optimization procedure based on genetic algorithm to the prediction of the electromagnetic fields scattered by weakly nonlinear dielectric objects. Formulation of the nonlinear scattering problem; Discussion on the heuristic hypotheses; Application of the genetic algorithm; Numerical results of some computer simulations; Conclusion.

Presents the general reflection rule for electromagnetic pole field on a plane interface between two media of different dielectric properties. Multipole reflection rule; Calculation of the reflected field; Results of the theory for multiple reflection rule; Conclusions.

Describes the dyadic Green's functions for an inhomogenous isotropic grounded slab embedded in an unbounded isotropic half-space. Characteristics of inhomegenous media properties in the propagation of electromagnetic fields; Derivation of the spectral electric Green's dyad; Discussion on numerical results.