Showing papers on "Computational electromagnetics published in 1997"
TL;DR: This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization, showing genetic-algorithm optimization to be suitable for optimizing a broad class of problems of interest to the electromagnetic community.
Abstract: This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided.
855 citations
01 Jan 1997
608 citations
TL;DR: The formulation combines the primitive function approach with five-point spatially sixth- and fourth-order methods to develop a fully discrete scheme for linear wave propagation phenomena with particular emphasis on computational electromagnetics in the time-domain.
112 citations
TL;DR: In this paper, a hybrid electromagnetic modeling and simulation environment is established for the analysis of complex structures which exhibit large variation in electrical size over their volume, using a combination of lumped-circuit elements, transmission lines, as well as three-dimensional (3-D) distributed electromagnetic models.
Abstract: The partial-element equivalent-circuit (PEEC) method is used to develop a flexible, hierarchical electromagnetic modeling and simulation environment for the analysis of noise generation and signal degradation mechanisms in packaged electronic components and systems. The circuit-oriented approach used by the method for the development of the numerical approximation of the electric-field integral equation leads to SPICE-compatible, yet fully dynamic, discrete approximation of the electromagnetic problem. Contrary to other full-wave formulations, the proposed method has the important attribute of lending itself to a very systematic and physical model complexity reduction on the basis of the electrical size of the various portions of the system. Thus, a hybrid electromagnetic modeling and simulation environment is established for the analysis of complex structures which exhibit large variation in electrical size over their volume, using a combination of lumped-circuit elements, transmission lines, as well as three-dimensional (3-D) distributed electromagnetic models. These models may or may not account for retardation, depending on the electrical size of the part of the structure that is being modeled. These special attributes of the proposed electromagnetic-simulation environment are demonstrated through several examples from its application to the modeling of noise interactions in generic interconnect and package geometries.
102 citations
TL;DR: In this article, the convergence of the higher-order quasi-linear approximations of the Born series is considered and a new approach is proposed to estimate the accuracy of the original QL approximation.
Abstract: We have recently introduced a quasi-linear (QL) approximation for the solution of the three-dimensional (3-D) electromagnetic modeling problem. In this paper we discuss an approach to improving its accuracy by considering the QL approximations of the higher-order. This approach can be considered the natural generalization of the Born series. We use the modified Green's operator with the norm less than 1 to ensure the convergence of the higher orders QL approximations to the true solution. This new approach produces the converged QL series, which makes it possible to estimate the accuracy of the original QL approximation without direct comparison with the rigorous full integral equation solution. It also opens principally new possibilities for fast and accurate 3-D EM modeling and inversion.
61 citations
TL;DR: In this paper, a time-domain method is developed which overcomes the computational difficulties associated with these convolutions, which is based on the z-transform from control and signal processing theory and the Z-domain model of the impedance.
Abstract: The impedance condition in computational aeroacoustic applications is required in order to model acoustically treated walls. The application of this condition in time-domain methods, however, is extremely difficult because of the convolutions involved. In this paper, a time-domain method is developed which overcomes the computational difficulties associated with these convolutions. This method builds on the z-transform from control and signal processing theory and the z-domain model of the impedance. The idea of using the z-domain operations originates from the computational electromagnetics community. When the impedance is expressed in the z-domain with a rational function, the inverse z-transform of the impedance condition results in only infinite impulse response type, digital, recursive filter operations. These operations, unlike convolutions, require only limited past-time knowledge of the acoustic pressures and velocities on the surface. Examples of one- and two-dimensional problems with and without flow indicate that the method promises success in aeroacoustic applications.
59 citations
TL;DR: A fictitious domain method is presented and implemented for time dependent problems of scattering by obstacles that allows us to work with uniform meshes for the electric field, independently of the geometry of the obstacle.
56 citations
TL;DR: The geometry independent MEI (GIMEI) is proposed which substantially improves the original MEI method and is used for capacitance extraction of general two-dimensional and three-dimensional very large scale integration (VLSI) interconnect.
Abstract: The measured equation of invariance (MEI) is a new concept in computational electromagnetics. It has been demonstrated that the MEI technique can be used to terminate the meshes very close to the object boundary and still strictly preserves the sparsity of the finite-difference (FD) equations. Therefore, the final system matrix encountered by the MEI is a sparse matrix with a size similar to that of integral equation methods. However complicated the Green's function, disagreeable Sommerfeld integrals, and very difficult umbilical meshes for multiconductors make the traditional MEI very difficult (if not impossible) to be applied to analyze multilayer and multiconductor interconnects. In this paper, the authors propose the geometry independent MEI (GIMEI) which substantially improves the original MEI method. The authors use GIMEI for capacitance extraction of general two-dimensional (2-D) and three-dimensional (3-D) very large scale integration (VLSI) interconnect. numerical results are in good agreement with published data and those obtained by using FASTCAP from Massachusetts Institute of Technology (MIT) and some other commercial tools, while GIMEIs are generally an order of magnitude faster than FASTCAP with much less memory usage.
55 citations
08 Jun 1997
TL;DR: For the first time, aggressive space mapping is applied to automatically align electromagnetic models based on hybrid mode-matching/network theory simulations with modelsBased on finite-element (FEM) simulations in design optimization of microwave circuits.
Abstract: For the first time, we apply aggressive space mapping to automatically align electromagnetic models based on hybrid mode-matching/network theory simulations with models based on finite-element (FEM) simulations in design optimization of microwave circuits. The parameter extraction phase of space mapping is given special attention. A statistical approach to parameter extraction involving l/sub 1/ and penalty concepts facilitates a key requirement by space mapping for uniqueness and consistency. Electromagnetic optimization of an H-plane resonator filter with rounded corners illustrates the advantages as well as the challenges of our approach.
47 citations
13 Nov 1997
TL;DR: It is shown that a recycled multipole-accelerated approach applied to recent model order reduction techniques requires nearly two orders of magnitude fewer floating point operations than direct techniques thus allowing the analysis of larger, more complex three-dimensional geometries.
Abstract: In this paper we describe a computationally efficient approach to generating reduced-order models from PEEC-based three-dimensional electromagnetic analysis programs. It is shown that a recycled multipole-accelerated approach applied to recent model order reduction techniques requires nearly two orders of magnitude fewer floating point operations than direct techniques thus allowing the analysis of larger, more complex three-dimensional geometries.
46 citations
01 Jan 1997
TL;DR: Numerical Linear Algebra, Multigrids, Domain Decomposition and Fictitious Domain Methods, and Numerical Schemes and CFD.
Abstract: Mathematical Analysis. Numerical Linear Algebra. Multigrids, Domain Decomposition and Fictitious Domain Methods. Numerical Schemes and CFD. Applications and CFD. Computational Physics and Chemistry. Computational Electromagnetics. Computational Elasticity and Structures. Optimization. Control. Computers and Systems.
TL;DR: In this paper, a hybrid formulation combining the method of moments (MOM) with the edge-based vector finite element method (FEM) is presented to solve electromagnetic radiation problems from structures consisting of an inhomogeneous dielectric body of arbitrary shape attached to one or more perfectly conducting bodies.
Abstract: A hybrid formulation is presented, which combines the method of moments (MOM) with the edge-based vector finite element method (FEM) to solve electromagnetic radiation problems from structures consisting of an inhomogeneous dielectric body of arbitrary shape attached to one or more perfectly conducting bodies. While either method alone fails to model these structures efficiently, a combination of both finite element and moment methods provides an excellent way to solve these problems. The FEM is employed to handle the interior domain of inhomogeneous dielectric bodies and the method of moments is used to develop surface integrals that relate the field quantities on boundary surfaces with the equivalent surface currents. These integral equations are then coupled to the finite element equations through the continuity of the tangential magnetic fields across the hybrid boundaries.
TL;DR: In this paper, a modified Lanczos scheme is presented for computing transient electromagnetic wavefields in inhomogeneous and lossy media. But the method is not suitable for two-dimensional (2-D) configurations.
Abstract: A new method for computing transient electromagnetic wavefields in inhomogeneous and lossy media is presented. The method utilizes a modified Lanczos scheme, where a so-called reduced model is constructed. A discretization of the time variable is then superfluous. This reduced model represents the transient electromagnetic wavefield on a certain bounded interval in time. Some theoretical aspects of the method are highlighted and numerical results showing the performance of the method for two-dimensional (2-D) configurations are given. Also, comparisons between this Lanczos method and the finite-difference time-domain (FDTD) method are made.
TL;DR: In this article, a method allowing coupling of static converters with electromagnetic devices represented by finite elements analysis is presented, with special attention paid to the fact that the state-variable equations of the static converter are automatically calculated.
Abstract: A method allowing coupling of static converters with electromagnetic devices represented by finite elements analysis is presented Special attention is paid to the fact that the state-variable equations of the static converter are calculated automatically These equations are then solved simultaneously with those of the electromagnetic structure, step by step with respect to time
25 May 1997
TL;DR: The authors model gaps in greater detail than is usually the case, and use the finite element method (FEM) to solve the resulting geometrically complex cell models, showing that simple models, such as equivalent cells, are sufficient for describing the behavior of small gap connected cell configurations exposed to dc electric fields.
Abstract: The interaction mechanisms of electromagnetic (EM) fields at very low frequencies remain elusive. To better understand the behaviour of cells in EM fields, the authors model configurations of gap-junction connected cells using the finite element method. Their results verify simplified models used to estimate transmembrane potential in chains of gap-connected cells, and suggest that more complex models are required to describe the frequency behaviour of chains of cells.
TL;DR: In this article, a bistatic k-space imaging concept for frequency-domain (FD) electromagnetic (EM) computer codes is presented, which enables the computation of images without the frequency sweep required for experimental images, resulting in a significant reduction in computational effort.
Abstract: A bistatic k-space imaging concept for frequency-domain (FD) electromagnetic (EM) computer codes is presented. The concept enables the computation of images without the frequency sweep required for experimental images, resulting in a significant reduction in computational effort. This analytical imaging technique uses bistatic radiation computed from a generalized radiation integral. Images permit physical insight and understanding into how a radiation or scattering pattern is produced, by decomposition of the resultant radiation into contributions from localized scattering centers, or hot spots. Knowledge of these hot spots permits a user to understand and modify the structure to obtain desired features.
TL;DR: In this paper, the authors used high density Hankel filters and a singularity extraction technique to circumvent the problem of the singularity of the Green's functions in the frequency domain.
Abstract: Three‐dimensional electromagnetic (EM) modeling in the frequency range from 100 kHz to about 200 MHz using integral equations is examined. The modeling algorithm is formulated in the frequency domain. Time‐domain responses for ground‐penetrating radar (GPR) and very early time time‐decaying transients are computed via Fourier transforms. Of vital importance to the modeling problem is the computation of the Hankel transforms in the Green's functions. The kernels of those Hankel transforms vary rapidly at high frequencies where displacement currents become important and are even singular for sources in the air, with poles approaching the real axis or branch cuts lying on the real axis. We use high density Hankel filters and a singularity extraction technique to circumvent these problems. Our modeling for GPR applications shows that dielectric targets are very obvious in radargrams, with waves reflected by target boundaries arriving at distinctive times, depending on the path they travel. While GPR signals a...
TL;DR: The utilization of the wavelets on [0,1] circumvents the difficulties in the application of theWavelets on the real line to finite-domain problems and has no periodicity constraint to the unknown function that is usually imposed by the periodic wavelets.
Abstract: An analysis of thin-wire antennas and scatterers using orthogonal wavelets on interval [0,1] is presented. The thin-wire version of the electric-field integral equation (EFLE) is solved by the hybrid wavelet expansion and boundary element method (HWBM). Maps between the curved solution domains and the interval [0,1] are established by using the geometrical representation of the boundary element method (BEM). By virtue of these maps, bases over the curved solution domains are derived from orthogonal wavelets on [0,1] that are used to expand the unknown current over the wires. The utilization of the wavelets on [0,1] circumvents the difficulties in the application of the wavelets on the real line to finite-domain problems and has no periodicity constraint to the unknown function that is usually imposed by the periodic wavelets. Numerical examples are provided for a variety of thin-wire antennas and scatterers.
TL;DR: In this paper, a numerical model for the computation of the electromagnetic field produced by an electrostatic discharge (ESD), occurring in the vicinity of a system of conducting objects, is presented.
Abstract: In this paper a numerical model for the computation of the electromagnetic field produced by an electrostatic discharge (ESD), occurring in the vicinity of a system of conducting objects, is presented. The ESD is modeled by a current flowing into a ionized channel located between two initially charged surfaces. The electromagnetic field generated by the ESD event is computed by means of a finite-difference time-domain (FDTD) algorithm based on the Yee's space-time mesh, and on the Mur's absorbing boundary conditions (ABC). A validation of the model by comparison against measured data is shown and an application to the analysis of the electromagnetic (EM) field produced by an ESD in a shielded box is presented.
08 Jun 1997
TL;DR: In this article, the electromagnetic wave propagation through semiconductor devices is modeled by coupling a physical electron-transport model, or a circuit approach, with Maxwell's equations, and the solution is developed in time-domain using Finite-Difference Time-Domain (FDTD) technique.
Abstract: This paper discusses the interactions between semiconductor devices and electromagnetic waves and the possible ways to interface modern devices and circuits in the mm-wave range. This topic is very important for advancing current MMIC designs and for developing futuristic devices and applications. The electromagnetic wave propagation through semiconductor devices is modeled by coupling a physical electron-transport model, or a circuit approach, with Maxwell's equations. The solution is developed in time-domain using Finite-Difference Time-Domain (FDTD) technique. Examples of device and circuit simulations are presented.
TL;DR: In this article, a numerical approach to the electromagnetic scattering of a plane wave impinging at skew incidence on the edge of a wedge with two different anisotropic face impedances is presented.
Abstract: A numerical approach to the electromagnetic scattering of a plane wave impinging at skew incidence on the edge of a wedge with two different anisotropic face impedances is presented. The diffracted field is obtained by applying the finite-difference (FD) method to solve two coupled parabolic equations. The solution obtained is valid in the high-frequency region.
03 Aug 1997
TL;DR: In this article, an analytical solution that can predict the near-field interaction between a scatterer and a rough surface is presented, using a recently developed technique which is based on the reciprocity theorem, K. Srabandi et al.
Abstract: In radar remote sensing of vegetation, accurate scattering models that can describe the interaction of electromagnetic waves and vegetation-covered terrain are of great importance. The common approach is to regard the vegetation-covered surfaces as a random collection of dielectric particles with canonical geometries, such as cylinders representing stems and branches and thin dielectric disks representing leaves, above a half-space dielectric medium with rough interface representing the ground. Most scattering models developed for this problem are based on single scattering properties of the scatterers. In these models, the scattering interaction among the vegetation particles and the vegetation particles and the rough surface are ignored. In more advanced models, such as radiative transfer (numerical or second-order iterative solutions), the scattering interaction among scatterers are accounted for assuming that the particles are in the far-field of each other. This is not an accurate model because most vegetation structures contain large particles (tree trunk, long branches, main stem for grasses) whose length are comparable to the vegetation layer thickness and are much larger than the wavelength. In these cases the near-field interaction, as opposed to far-field interaction, must be taken into account. Experimental results indicate that although the first-order scattering models are capable of predicting the co-polarized backscatter adequately, they are not able to predict the cross-polarized backscatter to within a desirable accuracy. In this paper, an analytical solution that can predict the near-field interaction between a scatterer and a rough surface is presented. This solution is derived using a recently developed technique which is based on the reciprocity theorem, K. Srabandi et al. (1994). This approach is very efficient since only the current distribution of isolated scatterers are needed to evaluate the interaction in the far-field region. The second moments of backscatter fields are provided for a circular dielectric cylinder above a slightly rough surface with inhomogeneous dielectric profile. The accuracy of the theoretical formulation is verified by conducting polarimetric backscatter measurements from a lossy dielectric cylinder above a slightly rough surface. Excellent agreement between the theoretical prediction and experimental results are obtained.
13 Jul 1997
TL;DR: A stable time domain solution technique which is based on advances in the understanding of the sources of the late instability problem and takes advantage of the distributed equivalent circuit representation of the electromagnetic problem effected through the use of partial element equivalent circuit (PEEC) models for the numerical approximation of the integral equation.
Abstract: Progress is being made towards the stable integration of time-domain electromagnetic field integral equations. Many different techniques have been proposed previously for overcoming the well known "late time" instability problem associated with the numerical integration of these equations. The instabilities could be either due to the discretization of the integral equation or the numerical integration scheme. In this paper, we present a stable time domain solution technique which is based on advances in the understanding of the sources of the late instability problem. The proposed technique takes advantage of the distributed equivalent circuit representation of the electromagnetic problem effected through the use of partial element equivalent circuit (PEEC) models for the numerical approximation of the integral equation. We are interested in solving problems associated with EMI and other EIP (electrical interconnect and package) induced noise effects. We are also interested in the simulation of complex RF and microwave circuits that involve both distributed and lumped circuits.
TL;DR: In this paper, a new numerical procedure is developed for the solution of the electric field integral equation (EFIE) for arbitrary-shaped microstrip structures, which decomposes the surface current density into divergenceless and curl-free parts which essentially get decoupled at the very low end of the frequency spectrum.
Abstract: A new numerical procedure is developed for the solution of the electric field integral equation (EFIE) for arbitrary-shaped microstrip structures. This approach is superior over conventional EFIE techniques particularly in the low-frequency region or where the structure to be analyzed is electrically small. A pair of new basis functions is presented which are essential to the solution in the entire frequency range of interest. The new basis functions decompose the surface current density into divergenceless and curl-free parts which essentially get decoupled at the very low end of the frequency spectrum. Typical numerical results are presented for certain examples to illustrate the difference in the results between the two methods.
TL;DR: In this article, a generalized coupled-dipole method was proposed to describe electromagnetic scattering by dielectric objects of arbitrary shape, where instead of a dipole moment there are an electric dipole, a magnetic dipole and an electric quadrupole, leading to an improved description of the scattered fields.
Abstract: A generalization of the coupled-dipole method introduced by Purcell Pennypacker [Astrophys. J.186, 705 (1973)], a low-frequency method used to describe electromagnetic scattering by dielectric objects of arbitrary shape, is proposed. At each site of the cubic lattice, instead of a dipole moment there are an electric dipole, a magnetic dipole, and an electric quadrupole, leading to an improved description of the scattered fields.
TL;DR: In this article, the generalized multipole technique (GMT) was combined with the method of moments (MoM) to analyze electromagnetic scattering problems, and the proposed hybrid method GMT-MoM improved the results obtained by GMT and reduced the computational effort in comparison with conventional MoM.
Abstract: Th method of moments (MoM) is combined with the generalized multipole technique (GMT) to analyze electromagnetic scattering problems. The proposed hybrid method GMT-MoM improves the results obtained by GMT and reduces the computational effort in comparison with conventional MoM techniques. Current density distributions have been obtained for a two dimensional scatterer illuminated by either a TM or TE near field source, showing the accuracy and effectiveness of this hybrid approach.
TL;DR: The complementary operators method (COM) as mentioned in this paper was developed for the purpose of canceling the reflections that arise from the artificial boundaries that terminate the computational domain in FDTD simulations, and five numerical experiments are presented to show the effectiveness and high efficiency of COM.
Abstract: The complementary operators method (COM) was developed for the purpose of canceling the reflections that arise from the artificial boundaries that terminate the computational domain in FDTD simulations. This article presents a discussion and an evaluation of COM. The theoretical background is developed in the analytical and discretized domains. Five numerical experiments are presented to show the effectiveness and high efficiency of COM. Applications to antenna radiation and absorbing boundary conditions are discussed.