Showing papers in "IEEE Transactions on Antennas and Propagation in 1996"
TL;DR: In this paper, a perfectly matched layer (PML) absorbing medium composed of a uniaxial anisotropic material is presented for the truncation of finite-difference time domain (FDTD) lattices.
Abstract: A perfectly matched layer (PML) absorbing material composed of a uniaxial anisotropic material is presented for the truncation of finite-difference time-domain (FDTD) lattices It is shown that the uniaxial PML material formulation is mathematically equivalent to the perfectly matched layer method published by Berenger (see J Computat Phys, Oct 1994) However, unlike Berenger's technique, the uniaxial PML absorbing medium presented in this paper is based on a Maxwellian formulation Numerical examples demonstrate that the FDTD implementation of the uniaxial PML medium is stable, equal in effectiveness as compared to Berenger's PML medium, while being more computationally efficient
1,326 citations
TL;DR: In this paper, an exact method for the calculation of the minimum radiation Q of a general antenna was derived, which is more straightforward than those previously published, and has implications on both the bandwidth and efficiency of antennas which fall into this category.
Abstract: An exact method, which is more straightforward than those previously published, is derived for the calculation of the minimum radiation Q of a general antenna. This expression agrees with the previously published and widely cited approximate expression in the extreme lower limit of electrical size. However, for the upper end of the range of electrical size which is considered electrically small, the exact expression given here is significantly different from the approximate expression. This result has implications on both the bandwidth and efficiency limitations of antennas which fall into this category.
978 citations
TL;DR: In this paper, a piecewise linear recursive convolution (PLRC) method is described that has greatly improved accuracy over the original RC approach but retains its speed and efficiency advantages.
Abstract: Electromagnetic propagation through linear dispersive media can be analyzed using the finite-difference time-domain (FDTD) method by employing the recursive convolution (RC) approach to evaluate the discrete time convolution of the electric field and the dielectric susceptibility function. The RC approach results in a fast and computationally efficient algorithm; however, the accuracy achieved is not generally as good as that obtained with other methods. A new piecewise linear recursive convolution (PLRC) method is described here that has greatly improved accuracy over the original RC approach but retains its speed and efficiency advantages.
513 citations
TL;DR: In this article, the perfectly matched layer (PML) technique is used for the simulation of free space with the finite-difference time-domain (FDTD) method, and the absorbing layer can be set very close to the structure, provided some specifications are satisfied.
Abstract: The wave-structure interactions are the most usual applications of the finite-difference method, in electromagnetic compatibility and radar cross-section computations. The aim of this paper is to get a detailed insight into the implementation of the perfectly matched layer (PML) technique when dealing with such important applications. The PML is a new technique developed for the simulation of free space with the finite-difference time-domain (FDTD) method. This paper deals with the application of this technique to the solution of wave-structure interaction problems. It is shown that the absorbing layer can be set very close to the structure, provided some specifications are satisfied, with the consequence that the computational requirements of the PML technique are far shorter than those of the other methods of free space simulation.
463 citations
TL;DR: In this paper, a new, circularly polarized small-size microstrip antenna using a proximity coupled feed method is proposed, and the measured results verify the circular polarization and the antenna radius was reduced by about 36% by using the slot lengths which are nearly equal to the diameter of the circular patch antenna.
Abstract: An antenna with a low profile, small size, and a light weight is required in mobile satellite communications. A new, circularly polarized small-size microstrip antenna using a proximity coupled feed method is proposed. A simple configuration based on a cross slot with unequal slot lengths on a circular patch is adopted to realize a small-size element antenna. The proposed antenna has no 90/spl deg/ hybrid coupler for circular polarization. The measured results verify the circular polarization, and the antenna radius was reduced by about 36% by using the slot lengths which are nearly equal to the diameter of the circular patch antenna. Good impedance and axial ratio characteristics have been obtained.
395 citations
TL;DR: A multilevel algorithm is presented for analyzing scattering from electrically large surfaces that accelerates the iterative solution of integral equations that arise in computational electromagnetics.
Abstract: A multilevel algorithm is presented for analyzing scattering from electrically large surfaces. The algorithm accelerates the iterative solution of integral equations that arise in computational electromagnetics. The algorithm permits a fast matrix-vector multiplication by decomposing the traditional method of moment matrix into a large number of blocks, with each describing the interaction between distant scatterers. The multiplication of each block by a trial solution vector is executed using a multilevel scheme that resembles a fast Fourier transform (FFT) and that only relies on well-known algebraic techniques. The computational complexity and the memory requirements of the proposed algorithm are O(N log/sup 2/ N).
364 citations
TL;DR: In this article, the authors introduce fractional-order multipoles of electric-charge densities and show that such multipoles effectively behave as intermediate sources bridging the gap between the cases of integer-order point multipoles such as point monopoles, point dipoles, and point quadrupoles, etc.
Abstract: Using the concept and tools of fractional calculus, we introduce a definition for "fractional-order" multipoles of electric-charge densities, and we show that as far as their scalar potential distributions are concerned, such fractional-order multipoles effectively behave as "intermediate" sources bridging the gap between the cases of integer-order point multipoles such as point monopoles, point dipoles, point quadrupoles, etc. This technique, which involves fractional differentiation or integration of the Dirac delta function, provides a tool for formulating an electric source distribution whose potential functions can be obtained by using fractional differentiation or integration of potentials of integer-order point-multipoles of lower or higher orders. As illustrative examples, the cases of three-dimensional (point source) and two-dimensional (line source) problems in electrostatics are treated in detail, and an extension to the time-harmonic case is also addressed. In the three-dimensional electrostatic example, we suggest an electric-charge distribution which can be regarded as an "intermediate" case between cases of the electric-point monopole (point charge) and the electric-point dipole (point dipole), and we present its electrostatic potential which behaves as r/sup -(1+/spl alpha/)/P/sub /spl alpha//(-cos/spl theta/) where 0
342 citations
TL;DR: In this paper, the authors proposed a calibration algorithm that estimates the calibration matrix consisting of the unknown gain, phase, and mutual coupling coefficients as well as the sensor positions using a set of calibration sources in known locations.
Abstract: High-resolution array processing algorithms for source localization are known to be sensitive to errors in the model for the sensor-array spatial response. In particular, unknown gain, phase, and mutual coupling as well as errors in the sensor positions can seriously degrade the performances of array-processing algorithms. This paper describes a calibration algorithm that estimates the calibration matrix consisting of the unknown gain, phase, and mutual-coupling coefficients as well as the sensor positions using a set of calibration sources in known locations. The estimation of the various parameters is based on a maximum likelihood approach. Cramer-Rao lower-bound (CRB) expressions for the sensor positions and the calibration matrix parameters are also derived. Numerical results are shown to illustrate the potential usefulness of the proposed calibration algorithm toward better accuracy and resolution in parametric array-processing algorithms.
309 citations
TL;DR: In this article, the microwave reflection coefficient measurements at 1.9 GHz and 4.0 GHz for a variety of typical smooth and rough exterior building surfaces are presented, including walls composed of limestone blocks, glass, and brick.
Abstract: This paper presents microwave reflection coefficient measurements at 1.9 GHz and 4.0 GHz for a variety of typical smooth and rough exterior building surfaces. The measured test surfaces include walls composed of limestone blocks, glass, and brick. Reflection coefficients were measured by resolving individual reflected signal components temporally and spatially, using a spread-spectrum sliding correlation system with directional antennas. Measured reflection coefficients are compared to theoretical Fresnel reflection coefficients, applying Gaussian rough surface scattering corrections where applicable. Comparisons of theoretical calculations and measured test cases reveal that Fresnel reflection coefficients adequately predict the reflective properties of the glass and brick wall surfaces. The rough limestone block wall reflection measurements are shown to be bounded by the predictions using the Fresnel reflection coefficients for a smooth surface and the modified reflection coefficients using the Gaussian rough surface correction factors. A simple, but effective, reflection model for rough surfaces is proposed, which is in good agreement with propagation measurements at 1.9 GHz and 4 GHz for both vertical and horizontal antenna polarizations. These reflection coefficient models can be directly applied to the estimation of multipath signal strength in ray tracing algorithms for propagation prediction.
265 citations
TL;DR: In this paper, a forward-backward approach was proposed for solving the magnetic field integral equation (MFIE) for perfectly conducting azimuthally homogeneous surfaces, including cases where the incident radiation has a lowgrazing angle.
Abstract: A new technique called "forward-backward," has been developed for solving the magnetic field integral equation (MFIE) for perfectly conducting azimuthally homogeneous surfaces, including cases where the incident radiation has a lowgrazing angle. The technique involves splitting both the surface current and the MFIE into two pieces; one representing primarily forwardly scattered energy and one representing primarily backwardly scattered energy. Each of the new integral equations can be solved by an iterative stepping procedure. The technique is applied to two sample problems–the classic Sommerfeld wedge and a peaked surface consisting of two filtered exponentials. The obtained solutions are shown to be accurate for each of these problems.
233 citations
TL;DR: In this article, a new implementation of the previously published mixed Fourier transform (MFT) method for including impedance boundaries in split-step parabolic equation solutions is described and demonstrated.
Abstract: A new implementation of the previously published mixed Fourier transform (MFT) method for including impedance boundaries in split-step parabolic equation solutions is described and demonstrated. The new algorithm is formulated entirely in the discrete domain which results in extended applicability and increased computation speed. A brief review of the original MFT solution is followed by a detailed description of the discrete formulation. The performance of the new algorithm is then demonstrated with a few examples which rely heavily on the accuracy of the impedance boundary. These examples include 10 MHz surface wave propagation over smooth and rough sea surfaces and 10 GHz calculations utilizing an effective rough surface impedance.
TL;DR: In this article, the authors illustrate the use of the Z transform in implementing the finite-difference time-domain (FDTD) method on materials which are dispersive or nonlinear, the relationship between the flux density and the electric field can be the most complicated part of the problem.
Abstract: In implementing the finite-difference time-domain (FDTD) method on materials which are dispersive or nonlinear, the relationship between the flux density and the electric field can be the most complicated part of the problem. Because the FDTD method is a sampled time-domain method, this relationship can be can be looked upon as a digital filtering problem. The Z transform is typically used in digital filtering and signal processing problems. The paper illustrates the use of the Z transform in implementing the FDTD method where complicated dispersive or nonlinear materials are involved.
TL;DR: In this paper, a uniform theory of diffraction (UTD) propagation model for a city street grid is presented, using the multiple image concept and the generalized Fermat's principle to describe the multiple reflections and diffractions.
Abstract: Presents a comprehensive uniform theory of diffraction (UTD) propagation model for a city street grid, using the multiple image concept and the generalized Fermat's principle to describe the multiple reflections and diffractions. The model is a quasi 3D one in the sense that the building walls are assumed to be much higher than the transmitter height so that the diffractions from the rooftops can be neglected. The model includes all possible specular wall and ground reflections and corner diffractions in the main street, side streets, and parallel streets of a microcell. This enables the signal propagation through all the possible paths to be tracked to the receiver at various line-of-sight (LOS) or out-of-sight (OOS) positions. Previous papers on such propagation models have included only a limited number of specular reflections and diffractions or they are restricted to a rectilinear grid where all the building walls on each side of the street are coplanar. Our model includes contributions to the received signal from all possible propagation paths, including ground and wall reflections from diffracted and specularly reflected signals both in the LOS and OOS regions. Within the scope of the UTD model, the accuracy of our model is limited mainly by the assumptions of characterizing the building walls as "smoothed-out" flat surfaces with average relative permittivity /spl epsiv//sub r/ and conductivity /spl sigma/. Our theoretical results of the signal path loss along the streets are compared with measurements which have been reported for city streets in Tokyo and New York City.
TL;DR: In this article, a new approach to solving the magnetic field integral equation (MFIE) for the current induced on a infinite perfectly conducting rough surface is presented, by splitting the propagator matrix into contributions from the left and from the right of the point of observation.
Abstract: A new approach to solving the magnetic field integral equation (MFIE) for the current induced on a infinite perfectly conducting rough surface is presented. By splitting the propagator matrix into contributions from the left and from the right of the point of observation, a second kind integral equation can be formed with a new Born term and a new kernel. Following discretization of this new integral equation, the unknown currents can be determined more rapidly and with significantly less storage requirements than conventional LU decomposition; where the time saving factor is roughly N/3 where N is the number of current samples on the surface and the usual storage requirements associated with matrix inversion are eliminated. While the new Born term is usually adequate for scattered field calculations, the new discretized integral equation can be iterated to amy desired accuracy with no apparent convergence problems. Results are presented for one-dimensional rough surfaces with rms heights exceeding one wavelength and rms slopes exceeding 40° which illustrate the robustness of the new Born term.
TL;DR: In this article, the authors derived a relation between the blockage width and the bistatic scattering width, and showed how cylinders such as struts and masts can be constructed to reduce their blockages.
Abstract: We discuss how forward scattering can he characterized in terms of an equivalent blockage width, and a relation between this and the bistatic scattering width is derived. Then, we show how cylinders such as struts and masts can be constructed to reduce their blockage widths. Thereby, when the cylinders are mounted in front of an antenna, the sidelobes and losses caused by the blockage will be reduced. For thin metal cylinders the blockage width reduction is obtained by giving its cross section an oblong shape and, in addition (for the TM case), by coating the outer metal surface with dielectric material to obtain a hard boundary condition. For thick cylinders, the reduced scattering is obtained by designing them as dielectric-filled parallel plate waveguides with the outer surfaces of the plates coated in the same way as for the thin struts. Dual-polarized performance is obtained in both cases by strip loading the outer surfaces. The performance of both the thin and the thick struts have limited frequency bandwidth. Both computed and measured results are presented; the computations being done with the moment method. The designs are based on the concept of soft and hard surfaces in electromagnetics, and the results can be regarded as a proof of the existence of hard surfaces for electromagnetic waves. The study considers reduction of forward scattering which also will give a reduction of the total integrated power of the scattered field over all directions-even backward.
TL;DR: In this article, an approach to far-field determination from phaseless measurements over two planar surfaces is described, analyzes, and implements an approach based on the global minimum of an appropriate functional, and a reliable iterative procedure converges on the solution regardless of the starting point.
Abstract: This paper describes, analyzes, and implements an approach to far-field determination from phaseless measurements over two planar surfaces. A proper formulation of the problem is considered as a quadratic inverse one whose data is the square amplitude of the near field. A solution is introduced as the global minimum of an appropriate functional. Next, to perform such a minimization procedure, a finite dimensional representation of the field radiated by sources whose plane-wave spectrum becomes negligible outside a fixed angular domain is used. A detailed investigation of the properties of the mapping connecting the unknowns to the data makes it possible to analyze how to escape from the local minima possibly met in the course of the minimization procedure. To this end, the crucial role of the availability of phaseless data over two different sarfa,ces and of appropriate weights in the functional definition is emphasized, and a reliable iterative procedure converging on the solution, regardless of the starting point, is thus obtained. This property is confirmed by experimental results concerning near-zone data from a shaped reflector at 9 Ghz. It can be readily appreciated that when only the field intensity is detected the complexity and the cost of the equipment required for near-field techniques in antenna testing and diagnostics can be reduced to a very large extent.
TL;DR: In this article, a stacked microstrip antenna with two parasitic elements, one increasing the impedance bandwidth and the other enhancing the gain, has been investigated experimentally, and the effects of each parasitic element have been clarified as well as the characteristics of the stacked three-element antenna.
Abstract: A stacked microstrip antenna with two parasitic elements, one of which increases the impedance bandwidth and the other which enhances the gain, has been investigated experimentally. The effects of each parasitic element have been clarified as well as the characteristics of the stacked three-element antenna and the design procedure for the stacked microstrip antenna have been described.
TL;DR: In this paper, an analytical model for polarizability dyadics of small chiral conductive particles in free space or those embedded in a lossy material is presented and discussed.
Abstract: An analytical model for polarizability dyadics of small chiral conductive particles in free space or those embedded in a lossy material is presented and discussed. Chiral particles are modeled by a wire loop connected to two straight wire elements. The electromagnetic analysis is based on the replacement of the particles by two connected antennas representing the wire and loop portions. Analytical expressions for polarizabilities are given. For electrically small particles, a lumped-element equivalent circuit can be constructed and the polarizabilities can be expressed in terms of equivalent circuit parameters. It is shown that the wire-and-loop antenna model for scatterers satisfies the reciprocity condition and other basic physical requirements. Approximate analytical expressions are compared with numerical simulations and with the experimental data on reflection from single chiral particles, and the results are seen to be in good agreement. The model can be used in analytical modeling of chiral and omega composite materials.
TL;DR: In this article, a fractal spatial arrangement of array elements and the fractal design of array factors is described for multiband operation. But the analysis is focused in two different approaches: the fractals spatial arrangement and array factor design.
Abstract: Most array factor design techniques are highly dependent on the operating wavelength. In this paper, a novel technique based on fractal structures is described for multiband operation. The analysis is focused in two different approaches: the fractal spatial arrangement of array elements and the fractal design of array factors. Although the patterns of fractal arrays show some interesting similarity properties at several bands, the directivity is not held constant through the bands. Nevertheless, such structures have been shown to be useful for designing low side-lobe arrays with equally weighted current elements. On the other hand, the fractal array factors presented do keep the same shape at several bands because they are designed as selfsimilar curves. The arrays that would synthesize such patterns present a characteristic power-law current distribution analogous to the spectral distribution of the bandlimited fractal Weierstrass function.
TL;DR: In this article, a systematic approach for the exact integration of general near-zone vector potentials associated with current-carrying circular loop antennas has been introduced, which leads to simple integrals which have closed form solutions for most commonly assumed loop current distributions.
Abstract: A direct integration procedure for far-zone vector potentials of thin circular loop antennas has been known for many years. This method is general in the sense that it leads to simple integrals which have closed form solutions for most commonly assumed loop current distributions. However, a comparable integration technique has not been available for evaluating the more complicated near-zone vector potentials. This paper introduces a systematic approach for the exact integration of general near-zone vector potentials associated with current-carrying circular loop antennas. A particular example is considered where this new integration technique is used to find exact solutions to the vector potential and electromagnetic field integrals for loops with a Fourier cosine-series expansion of the current. The observation is made that degenerate forms of these exact representations lead to simplified expressions for the important special cases of a uniform and cosinusoidal current loop. Two equivalent forms of exact series expansions are derived for the uniform current vector potential and field integrals. It is shown that the familiar small-loop approximations, as well as the classical far-field expressions, may be obtained as limiting cases of the more general exact series representations for the uniform current loop obtained in this paper. Convenient asymptotic far-field expansions are derived for the loop with a cosinusoidal current distribution. Finally, the far-field analysis for the cosinusoidal loop is generalized to loops having an arbitrary current represented by a Fourier cosine series.
TL;DR: A novel antenna design procedure based on genetic algorithm (GA) driven optimization is proposed and applied to the synthesis of wire antennas loaded with lumped components to design efficient ultra-broadhanld antennas and their corresponding matching networks.
Abstract: A novel antenna design procedure based on genetic algorithm (GA) driven optimization is proposed and applied to the synthesis of wire antennas loaded with lumped components. Loading circuit parameters, locations of the loads along the antenna, as well as matching network parameters, are optimized simultaneously. A computational scheme based on the Sherman-Morrison-Woodbury formula for the fast evaluation of the antenna performances for many distinct loading configurations is developed. The GA iteratively guides a population of randomly selected design candidates toward the optimal solution. The success of the proposed procedure is demonstrated through its application to the design of efficient ultra-broadhanld antennas and their corresponding matching networks.
TL;DR: In this paper, a technique to extract the 3D scattering center model of a complex target using the shooting and bouncing ray technique was presented, where the 3-D inverse synthetic aperture radar (ISAR) image of the target was generated based on a one-look ISAR algorithm.
Abstract: We present a technique to extract the three-dimensional (3-D) scattering center model of a complex target. Using the shooting and bouncing ray technique, we first generate the 3-D inverse synthetic aperture radar (ISAR) image of the target based on a one-look ISAR algorithm. In step two, we use the image processing algorithm CLEAN to extract the 3-D position and strength of the scattering centers from the 3-D ISAR image. Various implementation issues related to computation time and memory are addressed and an efficient scheme is presented to accomplish the 3-D scattering center extraction. Several examples ranging from simple canonical structures to complex targets are presented to demonstrate the validity of the extraction scheme and the usefulness of the resulting 3-D scattering center model.
TL;DR: In this article, an exact numerical model for scattering from a surface randomly rough in two directions is compared with experimental data, and a comparison of the absolute value of the bistatic scattering coefficient as normalized by the incident power shows the theory and experiment to be in good agreement.
Abstract: Predictions of an exact numerical model for scattering from a surface randomly rough in two directions are compared with experimental data. The numerical model is based on Monte Carlo simulation using an iterative version of the method of moments known as the sparse-matrix flat-surface iterative approach (SMFSIA). Experimental data is obtained from millimeter wave laboratory experiments in which the bistatic scattering patterns of fabricated surfaces with known statistical parameters were measured. The surfaces studied have both a Gaussian height distribution and correlation function, so that their statistics are characterized by an rms height and correlation length. An rms height of 1 wavelength and correlation lengths ranging from 1.41-3 wavelengths are investigated in this paper, and the phenomenon of backscattering enhancement is observed both in the numerical predictions and experimental data. A comparison of the absolute value of the bistatic scattering coefficient as normalized by the incident power shows the theory and experiment to be in good agreement.
TL;DR: In this paper, a technique for replacing the signals from failed elements in a digitally beamformed receive array is presented, which does not impose special restrictions on the correlation properties of the received signals.
Abstract: A technique is presented for replacing the signals from failed elements in a digitally beamformed receive array. The technique is shown to be useful in a multiple signal environment and does not impose special restrictions on the correlation properties of the received signals. Experimental data confirm the operation of this algorithm for the case of one signal and one interfering source. The technique is shown to be accurate when the incident signal locations are not precisely known, and even when the signals are distributed over a broad angular region or are only known to be located within a broad angular region.
TL;DR: In this article, five different designs for broad-band monopole antennas are evaluated for pulse radiation and various quantities characteristic of their pulsed performance are computed, including reflected voltage in the feeding transmission line, radiated electric field, radiating efficiency, time-domain gain, fidelity, and symmetry when the monopoles are excited by a differentiated Gaussian pulse.
Abstract: Five previously proposed designs for broad-band monopole antennas are evaluated for pulse radiation. These designs use continuous resistive loading and/or discrete capacitive loading to increase the bandwidth over that of a simple, metallic monopole. The parameters for each of the designs are scaled so that the designs can be compared on a common basis (frequency range). Each of the antennas is analyzed numerically, and quantities characteristic of their pulsed performance are computed. These quantities include the reflected voltage in the feeding transmission line, radiated electric field, radiating efficiency, time-domain gain, fidelity, and symmetry when the monopoles are excited by a differentiated Gaussian pulse. In addition, the input reflection coefficient and gain at broadside for monochromatic excitation are shown. Explanations are provided for the differences in performance for these designs.
TL;DR: In this paper, a systematic comparison of various aperture shapes for the aperture coupled rectangular microstrip antenna has been carried out and an optimum "hour glass"-shaped aperture configuration has been proposed for maximum coupling.
Abstract: Aperture shape and size are the crucial parameters for the aperture coupled microstrip antennas (ACMSA). A systematic comparision of various aperture shapes for the aperture coupled rectangular microstrip antenna has been carried out. An optimum "hour glass"-shaped aperture configuration has been proposed for maximum coupling.
TL;DR: In this paper, the authors present two aspects of resonant microstrip patch antennas, namely, miniaturization and resonant frequency tuning, which allows a controllable size reduction over a limited range.
Abstract: The paper addresses two aspects of resonant microstrip patch antennas, namely, miniaturization and resonant frequency tuning. First, a patch geometry which allows a controllable size reduction over a limited range is presented. The basic shape is circular with slits cut into it. Modification of the slit geometry leads to both linear as well as circular polarized (CP) operation. Second, the use of another patch of a specific shape as a superstrate layer in a stacked configuration allows tuning over a relatively large frequency range as compared to the patch bandwidth. Tuning is accomplished by a simple rotation of the superstrate layer. The use of another superstrate layer allows tunable CP operation. Details on the antenna characteristics have been worked out for two examples, and computations have been compared with measurements where possible. Some design guidelines have also been included.
TL;DR: In this paper, the authors used the method of moments to analyze short-pulse plane-wave scattering from perfectly conducting bodies of revolution buried in a lossy, dispersive half space.
Abstract: The method of moments is used to analyze short-pulse plane-wave scattering from perfectly conducting bodies of revolution buried in a lossy, dispersive half space. The analysis is performed in the frequency domain, with the time-domain fields synthesized via Fourier transform. To make this analysis efficient, the method of complex images is used to compute the frequency-dependent components of the half-space dyadic Green's function. Results are presented for short-pulse scattering from buried spheres and cylinders, using measured frequency-dependent soil parameters (permittivity and conductivity).
TL;DR: In this article, a single-layer dual-band frequency selective surface (FSS) created by the perturbation of a single band dipole array is studied and a simple algebraic formulation is derived to analyze both element and spacing perturbations.
Abstract: A single-layer dual-band frequency selective surface (FSS) created by the perturbation of a single-band dipole array is studied. A simple algebraic formulation is derived to analyze both element and spacing perturbations. Guidelines are then proposed to allow dual-band FSSs to be designed with no anomalous behavior occurring in the two desired bandstop responses. Examples of unsuccessful and successful dual-band FSSs are calculated.
TL;DR: Numerical results obtained with a nonparallelized computer code are presented, which emphasize the superiority of this technique in terms of memory storage requirements and computing times over the standard finite element approach, as well as over the rigorous hybrid finite element-integral equation formulation.
Abstract: A nonoverlapping domain decomposition method is proposed for the finite element solution of the scattering problem by electrically large, inhomogeneous, infinite cylinders of arbitrary cross section. To minimize the size of the total computational domain, a second-order-absorbing boundary condition (ABC) is applied upon an outer boundary of arbitrary shape which may be conformal to the surface of the scatterer. This domain is then partitioned into concentric subdomains circumscribing the object. A second-order transmission condition, derived from the ABC, is prescribed upon the interfaces between two adjacent subdomains. This particular configuration is responsible for the fast convergence of the domain decomposition iterative algorithm, which is parallelizable. Numerical results obtained with a nonparallelized computer code are presented, which emphasize the superiority of this technique in terms of memory storage requirements and computing times over the standard finite element approach, as well as over the rigorous hybrid finite element-integral equation formulation.