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Showing papers in "Electromagnetics in 2003"


Journal ArticleDOI
TL;DR: In this paper, the real parts of both the permittivity and the permeability are altered from positive to negative, and the reflection and the transmission coefficients suffer phase reversals without change in their respective magnitudes.
Abstract: Two results about the planewave response of an isotropic, dielectric-magnetic, homogeneous, planar slab are deduced when the real parts of both the permittivity and the permeability are altered from positive to negative. First, the reflection and the transmission coefficients suffer phase reversals without change in their respective magnitudes. Second, the Goos–Hanchen shifts experienced by beams on total reflection reverse their directions.

119 citations


Journal ArticleDOI
TL;DR: In this article, experimental evidence of the non-reciprocal Tellegen magnetoelectric effect is presented, where the measured particle consists of a small ferrite sphere and a small piece of a thin metal wire glued to the sphere.
Abstract: Experimental evidence of the nonreciprocal Tellegen magnetoelectric effect is presented. The measured particle consists of a small ferrite sphere and a small piece of a thin metal wire glued to the sphere. The whole system is magnetized by a permanent magnet. The Tellegen effect was observed experimentally when this particle was positioned in a rectangular waveguide and excited by a small wire loop. This result experimentally confirms by a direct observation in the microwave range the known theoretical conclusions and experimental evidences at low frequencies regarding mistakes in some theoretical papers that claimed nonexistence of the Tellegen effect.

59 citations


Journal ArticleDOI
TL;DR: In this article, the performance of periodic electromagnetic band-gap (EBG) structures composed of complex scatterers of dielectrics and conductors of arbitrary configurations is analyzed using the finite difference time domain (FDTD) full wave analysis technique with periodic boundary conditions/perfectly matched layers integrated with the Prony method.
Abstract: The main challenge in this paper is to provide an efficient and powerful computational engine to effectively characterize the performance of periodic electromagnetic band-gap (EBG) structures composed of complex scatterers of dielectrics and conductors of arbitrary configurations. The finite difference time domain (FDTD) full wave analysis technique with periodic boundary conditions/perfectly matched layers (PBCs/PMLs) integrated with the Prony method is applied to accurately obtain the interactions of EM waves with the periodic band-gap structures and detail their broadband behaviors. The split-field approach is used to discretize the Floquet-transformed Maxwell's equations derived in the periodic structures. The developed engine is successfully applied to characterize and create insight into the electromagnetic performances of different classes of challenging EBG structures in the areas of frequency selective surfaces (FSSs), dielectric band-gap materials, and left-handed (LH) composite meta-materials. ...

51 citations


Journal ArticleDOI
TL;DR: In this paper, the conductivity of conducting polyaniline composites in the radio frequency range X, Ku, and Ka bands is investigated and methods for determining the conductivities and the shielding effectiveness are discussed.
Abstract: Electromagnetic interference behaviour of conducting polyaniline composites in the radio frequency range X, Ku, and Ka bands is presented. Methods for determining the conductivity and the shielding effectiveness are discussed. The conducting composites are made from CSA-doped polyaniline blended with the styrene acrylonitrile host polymer. The samples exhibit high conductivities, up to 104 S.m−1, and therefore are compatible with an electromagnetic shielding application. The percolation threshold is very low—below 1% of mass fraction of polyaniline in the blend—and the shielding effectiveness is up to 70 dB, depending on the sample.

37 citations


Journal ArticleDOI
TL;DR: In this article, an efficient technique to reconstruct the field radiated by an antenna in the far field region from the knowledge of the nonuniformly spaced plane-polar data measured by a probe in the near-field region is developed.
Abstract: An efficient technique to reconstruct the field radiated by an antenna in the far-field region from the knowledge of the nonuniformly spaced plane-polar data measured by a probe in the near-field region is developed in this work. The singular value decomposition method is applied to evaluate the uniformly distributed samples, whose positions are fixed by a nonredundant sampling representation of the field. Then the plane-rectangular near-field data needed to perform the classical probe-compensated near-field-far-field transformation are efficiently evaluated via the optimal sampling interpolation algorithm. As demonstrated by numerical tests, the far-field reconstruction process is accurate and stable

30 citations


Journal ArticleDOI
TL;DR: In this paper, a new method was proposed for injecting plane waves (although not constrained solely to plane waves) into the computational domain of a finite-difference time domain (FDTD), where fields from a background FDTD space were used to calculate the equivalent currents on a rectangular boundary such that the currents so defined satisfy the discrete curl operator of FDTD.
Abstract: A new method is proposed for injecting plane waves (although not constrained solely to plane waves) into the computational domain of a finite-difference time domain (FDTD). Fields from a background FDTD space that can support perfect plane waves traveling at an arbitrary angle of incidence are used to calculate the equivalent currents on a rectangular boundary such that the currents so defined satisfy the discrete curl operator of FDTD. When these equivalent currents are copied onto another FDTD domain, the rectangular boundary acts as a perfect teleportation window, inside of which the plane wave exists and outside of which no fields are produced. Thus a scatterer within the window is illuminated with a perfect plane wave and its scattered fields exit transparently through the window. Thus a total field-scattered field FDTD formulation is attained automatically. This method correctly accounts for the nonlinear grid dispersion created by the discretization of the Yee grid. The only error in the plane wave...

21 citations


Journal ArticleDOI
TL;DR: In this paper, the rotating waves in a Laplace domain were introduced for formulating and solving wave problems with wedge-shaped configurations, and applications of this method were concerned with the diffraction by isorefractive (or diaphaneous) wedges.
Abstract: We introduce the rotating waves in a Laplace domain for formulating and solving wave problems with wedge-shaped configurations. The method we develop is alternative to and possibly simpler than the one of Malyuzhinets. Applications of this method in this paper are concerned with the diffraction by isorefractive (or diaphaneous) wedges.

19 citations


Journal ArticleDOI
TL;DR: In this article, a periodic Green's function-based method for computing the static effective permittivity of metallic crystals is proposed, where the homogenization problem can be reduced to an integral equation over the boundary of a generic metallic inclusion.
Abstract: In this paper, we propose a periodic Green's function–based method for computing the static effective permittivity of metallic crystals. The method is valid for arbitrary lattice structures and inclusion shapes. We show that the homogenization problem can be reduced to an integral equation over the boundary of a generic metallic inclusion. The kernel of the integral equation is a periodic Green's function. This Green's function corresponds to the static potential from a three-dimensional array of point charges plus a uniform density of charge. Different representations of the Green's function are presented and discussed. We apply the developed formalism to characterize the effective permittivity of a three-dimensional array of thin metallic wires.

19 citations


Journal ArticleDOI
TL;DR: In this paper, a closed-form spatial Green's function for finite dielectric structures was derived by employing a combination of the characteristic Green's functions and complex images (CI) techniques.
Abstract: A novel technique to derive the closed-form spatial Green’s function for finite dielectric structures is presented by employing a combination of the characteristic Green’s function (CGF) and complex images (CI) techniques. To show the versatility of this technique, a two-dimensional finite dielectric substrate is studied in detail. Since the structure is nonseparable, the derived Green’s function is an approximate solution especially in the corners. It is shown that by applying certain corrections on the reflection coefficient of the fields at edges, more accurate results are obtained. The derived Green’s function exhibits excellent agreement with the available rigorous method of moments solution of the problem.

18 citations


Journal ArticleDOI
TL;DR: In this article, a numerical approach for ray congruences in the presence of multiple diffraction from objects with polygonal flat facets is presented. But this approach is limited to the case of objects with oblique straight edges.
Abstract: Ray tracing, taking reflection and diffraction into account, is employed together with asymptotic techniques for electromagnetic analysis of large and complex objects. This paper introduces a novel approach in numerical ray tracing providing analytical models for ray congruences in the presence of multiple diffraction from objects with polygonal flat facets. A general arrangement of oblique straight edges is examined. Functionals relating crossing points of ray paths on consecutive diffracting edges have been developed. Higher order diffraction has been treated resorting to an approximate method, which is able to locate diffracting points on the edges with desired accuracy.

18 citations


Journal ArticleDOI
TL;DR: In this article, a high-order method of moment (HO-MoM) solution of the combined field integral equation is presented for the solution of RCS of piecewise homogeneous penetrable bodies.
Abstract: A high-order method of moment (HO-MoM) solution of the combined-field integral equation is presented for the solution of the RADAR cross-section (RCS) of piecewise homogeneous penetrable bodies. The high-order method is based on a point-matched formulation with quadrature point sampling. It is demonstrated that the proposed method realizes true high-order convergence for the surface equivalent current densities and the RCS for a number of canonical problems.

Journal ArticleDOI
TL;DR: The multilevel fast multipole algorithm (MLFMA) is incorporated to speed up the solution of the resultant matrix system, thereby leading to a grid-robust, higher-order MLFMA solution having an O(N log N) computational complexity, where N denotes the total number of unknowns.
Abstract: Recently, a set of novel, grid-robust, higher-order vector basis functions were proposed for the method-of-moments (MoM) solution of integral equations of scattering. The evaluation of integrals in the MoM is greatly simplified due to the unique properties associated with these basis functions. Moreover, these basis functions do not require the edge of a given patch to be completely shared by another patch; thus, the resultant MoM is applicable even for defective meshes. In this article, these new basis functions are employed to solve integral equations for three-dimensional (3-D) mixed dielectric/conducting scatterers. The multilevel fast multipole algorithm (MLFMA) is incorporated to speed up the solution of the resultant matrix system, thereby leading to a grid-robust, higher-order MLFMA solution having an O(N log N) computational complexity, where N denotes the total number of unknowns. Numerical examples are presented to demonstrate the accuracy of the proposed method.

Journal ArticleDOI
TL;DR: In this paper, both general and specific harmonic-balance equations of induction machines are discussed, where the general equations refer to asymmetrical machines and the specific ones are valid for only symmetrical machines, with no parallel branches.
Abstract: Derivation of both general and specific harmonic-balance equations of induction machines is outlined. Whereas the general equations refer to asymmetrical machines, the specific ones are valid for only symmetrical machines, with no parallel branches. They allow to classify all the symmetrical machines into three categories. The classification is also useful for machines not strictly fulfilling the assumptions for the validity of the specific equations. Categories as well as slot harmonic frequencies, listed in six tables and referring to the machines with one through six pole-pairs, conclude the paper.

Journal ArticleDOI
TL;DR: In this paper, an exact expression for the radiated EM fields due to a multiconductor transmission line structure with a wire or ground plane as a return path has been presented, where coupled equations describing the system have been decomposed to find the current along the lines, and then a time-domain approach has been used to derive radiated fields.
Abstract: An exact expression for the radiated EM fields due to a multiconductor transmission line structure with a wire or ground plane as a return path has been presented. First the coupled equations describing the system have been decomposed to find the current along the lines, and then a time-domain approach has been presented to derive the radiated fields. It has been shown that the radiated field can be expressed as a function of the voltages and currents in the terminals.

Journal ArticleDOI
TL;DR: In this article, the strong propertyfluctuation theory (SPFT) is formulated for cubically nonlinear, isotropic chiral composite mediums and convergence is established at the level of the bilocally approximated SPFT, with respect to both linear and nonlinear properties.
Abstract: The strong-property-fluctuation theory (SPFT) has gained prominence in the homogenization of linear composite mediums. Through accommodating the distributional statistics of the component phases, the SPFT takes account of coherent scattering interactions at subwavelength length scales and thereby represents a significant improvement over conventional homogenization approaches. We formulate the SPFT here for cubically nonlinear, isotropic chiral composite mediums. The bilocally and trilocally approximated SPFT (i.e., the second- and third-order SPFT, respectively) are developed from the corresponding linear theories, using Maclaurin expansions to accommodate nonlinear behavior. By means of a numerical example, convergence is established at the level of the bilocally approximated SPFT, with respect to both linear and nonlinear properties. The phenomenon of nonlinearity enhancement is explored.

Journal ArticleDOI
TL;DR: In this article, a combination of a direct subgrid technique with a locally conformal finite difference time domain (FD-TD) algorithm for arbitrarily shaped perfect conductors, and with a modified intersection approach for arbitrary dielectric boundaries is described.
Abstract: Advanced techniques for the finite difference time domain (FD-TD) method are described, which improve the efficiency of the simulation of three-dimensional (3D) microwave components, including structures of more general shape. The formulations are based on a combination of a direct subgrid technique with a locally conformal FD-TD algorithm for arbitrarily shaped perfect conductors, and with a modified intersection approach for arbitrary dielectric boundaries. The involved subgrid technique, where a main grid is directly orthogonalized against a dual grid, avoids the usual necessity of additional interpolation terms. Application of the matrix pencil method reduces the number of required time steps. Advantages of the combined techniques are high accuracy, flexibility, and efficiency concerning both storage capacity and CPU time. Their versatility for the CAD of 3D microwave structures is demonstrated with typical examples, like coax feed with dielectric coating, dielectric resonator filter, and waffle-iron ...

Journal ArticleDOI
TL;DR: In this article, the alternating direction implicit finite difference time domain (ADI-FDTD) method and the method of moments in the time domain were combined to analyze problems involving thin-wire antennas close to inhomogeneous dielectric bodies.
Abstract: This paper describes a new hybrid technique, combining the alternating direction implicit finite difference time domain (ADI-FDTD) method and the method of moments in the time domain (MoMTD) to analyze problems involving thin-wire antennas close to inhomogeneous dielectric bodies. The unconditionally stable ADI-FDTD formulation presents computational advantages over the explicit Yee FDTD scheme in cases that require a fine mesh to accurately model their electromagnetic characteristics. The hybrid procedure has been found stable in the examples analyzed so far, which was not always the case in the previous approach based on the classical Yee FDTD.

Journal ArticleDOI
TL;DR: In this article, the problem of the coupling of a surface dielectric grating to a structurally chiral volume grating is formulated and solved, where the volume grater is a chiral sculptured thin film, which exhibits the circular Bragg phenomenon in distinct wavelength regimes.
Abstract: The problem of the coupling of a surface dielectric grating to a structurally chiral volume grating is formulated and solved. The volume grating is a chiral sculptured thin film, which exhibits the circular Bragg phenomenon in distinct wavelength regimes. Two distinct interactions are involved: (i) those of linearly polarized and circularly polarized modes, and (ii) those of nonspecular modes with the specular Bragg phenomenons. Numerical studies show that the circular Bragg phenomenon is virtually immune to the presence of the surface grating. Hence, chiral STF filters can be diffraction-coupled to other optical elements.

Journal ArticleDOI
TL;DR: In this article, Fang et al. compared Fang's (4,4) and Yee's (2,2) FDTD schemes in terms of computational efficiency in the presence of metallic and dielectric boundaries.
Abstract: Fang’s fourth-order finite-difference time-domain (FDTD) schemes are compared with conventional second-order Yee’s FDTD scheme in terms of computational efficiency. A three-dimensional (3D) rectangular cavity partially filled with a dielectric material is considered for the numerical experiments. A set of numerical boundary conditions, constructed consistently with the higher order accuracy of the schemes, enables a realistic assessment of the computational efficiencies of Fang’s (4,4) and (2,4) schemes in the presence of metallic and dielectric boundaries. Numerical results show that both Fang’s (4,4) and (2,4) schemes are more efficient than Yee’s (2,2) scheme by more than two orders of magnitude in CPU time for a fixed error level in the L 2 norm. This comparative study verifies that Fang’s explicit fourth-order FDTD methods, complemented with the proposed numerical boundary conditions at planar material interfaces, yield very accurate and computationally very efficient time-domain solvers for the nume...

Journal ArticleDOI
TL;DR: In this paper, the electromagnetic field in an isotropic (dielectric-magnetic) medium that is arbitrarily nonhomogeneous can be represented in terms of two vector potentials that are solutions of a system of two second-order partial differential equations.
Abstract: We show that the electromagnetic field in an isotropic (dielectric–magnetic) medium that is arbitrarily nonhomogeneous can be represented in terms of two vector potentials that are solutions of a system of two second-order partial differential equations. Furthermore, we derive conditions that permit the reduction of the two vector potentials to a pair of collinear single components and we establish a connection to an alternative solution formalism in terms of scalar Hertz potentials. The reduction involves both the vector potentials and their sources.

Journal ArticleDOI
TL;DR: In this article, a general solution of the thin wire circular loop radiation is offered, without assuming a certain current distribution in advance, and the solution is valid for any radius-wavelength ratio and for both near and far field.
Abstract: A general solution of the thin wire circular loop radiation is offered, without assuming a certain current distribution in advance. The solution is valid for any radius-wavelength ratio and for both near and far field. The field potentials are expressed through the general wave equation basis functions in spherical coordinate system. A zero electric field along the loop is achieved as a sum of the radiation field and time-independent excitation field. The unknown-expansion coefficients are found by the Galerkin method. For highly accurate fulfillment of the boundary condition only twelve modes were required. The current distribution was found uniform for a very small loop, but also close to uniform for certain much larger electric lengths. It was also found that in a far zone both E ϕ and E θ exist, with E ϕ being some ten times greater than E θ, if the source occupies a very small portion of the loop.

Journal ArticleDOI
TL;DR: In this article, the behavior of the magnetic polarizability for two circular apertures in parallel conducting planes is investigated, and the scattered potentials are expressed in terms of discrete and continuous modes based on the eigenfunction expansion and Hankel-transform.
Abstract: The behavior of the magnetic polarizability for two circular apertures in parallel conducting planes is investigated. The scattered potentials are expressed in terms of discrete and continuous modes based on the eigenfunction expansion and Hankel-transform. The boundary conditions are used to derive a set of simultaneous equations for the discrete modal coefficients. A fast convergent series representation for the magnetic polarizability is presented. The magnetic polarizability is calculated to illustrate the behavior of a magnetostatic potential penetration into apertures in terms of aperture geometry.

Journal ArticleDOI
TL;DR: In this article, the authors consider a variety of numerical and physical properties that can be used as benchmarks for numerical solutions of transient and ultrawideband scattering problems and highlight several properties that are important in the design of a good numerical scheme.
Abstract: In this paper we consider a variety of benchmarks for numerical solutions of transient and ultrawideband scattering problems. We highlight a number of numerical and physical properties that can be used as benchmarks and that are important in the design of a good numerical scheme. We review a class of scattering problems, involving plane-wave excitation, for which a semi-analytic solution may be derived via the method of regularization. We introduce a novel scattering problem, involving dipole excitation, for which a semi-analytic solution may also be derived.

Journal ArticleDOI
TL;DR: In this article, the TEM-mode transmission line theory and the quasi-static theory are applied in the analysis of electric field distributions inside the simulator, and results of transient electric fields and field distributions for well-matched and mismatched conditions are presented, respectively.
Abstract: The time-domain moment method (TDMM) is used to calculate the transient electric fields and field distributions inside a large wire-array NEMP simulator. The TEM-mode transmission-line theory and the quasi-static theory are applied in the analysis of electric field distributions inside the simulator. Results of transient electric fields and field distributions for well-matched and mismatched conditions are presented, respectively. In the study of the quasi-static field, it is found that the electric field in the working volume appears without any distortion. In an analysis of the TEM-mode condition, it is found that the distortion wave form of the electric field is greatly affected by the refection coefficients at both the source side and terminating end. But it is also found that the electric field is almost homogeneously distributed inside the working volume of the simulator for both well-matched and mismatched conditions. Outside the working volume, electric field increases as the field point approache...

Journal ArticleDOI
TL;DR: In this paper, two different methods for implementing a new thin-slot finite-difference time-domain (FDTD) subcell model are presented, and the effect of the wall thickness on the field penetration is clearly demonstrated.
Abstract: Two different methods for implementing a new thin-slot finite-difference time-domain (FDTD) subcell model are presented in this paper. Comparisons are performed with existing models in the literature, as well as with measurements for Shielding Effectiveness (SE) of cavities. The proposed methods are shown to exhibit superior accuracy, especially at lower frequencies. Furthermore, to model the thickness of the cavity walls more accurately, a comparative study of three existing one-dimensional thin-layer algorithms is performed, and one of them is selected, generalized, and applied to three-dimensional SE predictions. The effect of the wall thickness on the field penetration is clearly demonstrated.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the applications of discrete-time signal processing (SP) techniques for the purpose of generating accurate plane waves in the finite-difference time-domain (FDTD) method.
Abstract: We demonstrate the applications of discrete-time signal-processing (SP) techniques for the purpose of generating accurate plane waves in the finite-difference time-domain (FDTD) method. The SP techniques are used either to reduce the high-frequency content of the source excitation or to compute more precise incident-field values in the computational domain. The effects of smoothing windows of various lengths, digital lowpass filters of various bandwidths and characteristics, and polynomial interpolation schemes of various orders are investigated. Arbitrary signals with multifrequency content are considered.

Journal ArticleDOI
TL;DR: In this article, the applicability of the computational technique called the method of auxiliary sources (MAS) to the calculation of the transition radiation is attempted. But it is not shown how to apply the MAS to each separate component.
Abstract: An investigation of the applicability of the computational technique called the method of auxiliary sources (MAS) to the calculation of the transition radiation is attempted. The following two problems have been dealt with. The first one refers to the interaction of a relativistic electron with a dielectric sphere, whereas the second one refers to the interaction of a relativistic electron with a metallic oblate spheroid. The incident wave associated with the electron is dissolved into spectral components and then the boundary value problem is formulated by applying the MAS to each separate component. Convergence tests and comparisons of the predictions with previous analytical treatments and experimental results are presented. Subsequently the applicability of MAS is clarified.

Journal ArticleDOI
TL;DR: This paper shows that by means of an appropriate optimization technique the zeros of Ludwig patterns can be perturbed so as to improve or modify pattern and/or aperture distribution characteristics without altering the wide-angle decay behavior.
Abstract: This is an Accepted Manuscript of an article published by Taylor & Francis in Electromagnetics on January of 2003, available online: http://www.tandfonline.com/10.1080/02726340390159414

Journal ArticleDOI
TL;DR: In this paper, the magnetic field boundary condition on the dipoles of two arbitrarily located parallel cylindrical dipoles is derived by imposing the electric field continuity conditions on the physical surface of each dipole.
Abstract: In this paper, the radiation from two arbitrarily located parallel cylindrical dipoles is analyzed on the basis of the method of auxiliary sources (MAS). This method is applied by introducing sets of fictitious sources, which are located inside the dipoles, for the direct description of the radiated electromagnetic (EM) field. The unknown currents of the sources are determined by imposing the electric field continuity conditions on the physical surface of each dipole. The presented solution is formed using spatially overlapped sinusoidal dipoles instead of elementary dipoles that are usually used in conventional implementations of the MAS. Since the currents of the fictitious sources are determined, the current distributions on the dipoles can be obtained by invoking the magnetic field boundary condition. After that, the self- and the mutual admittances/impedances of the dipoles are readily computable. Several examples are presented for various geometrical arrangements of the two-element array. In each ca...

Journal ArticleDOI
TL;DR: In this paper, a weighting function is provided to control the relative error along the re-optimized array pattern with multiple wideband null steering when arbitrary element failures occur, and the results indicate that only a few elements are needed for the compensation.
Abstract: This paper deals with re-optimizing linear array patterns with multiple wideband null steering when arbitrary element failures occur. Using partial controlled arrays, the re-optimization method is formulated as a minimax problem solved by a linear programming technique. A weighting function is provided to control the relative error along the re-optimized array pattern. The results indicate that only a few elements are needed for the compensation. Furthermore, the suppressed sectors and the SLL can be improved by increasing the number of controlled elements. The results validate the capability of the proposed method to compensate for arbitrary element failures to re-create the multiple wideband nulls.