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Title: Full July 2007 Journal
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
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Title: Front/Back Matter
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 563 KB

Title: Numerical Examinations of the Stability of FDTD Subgridding Schemes
Abstract: The stability of two-dimensional Finite-Difference Time-Domain subgridding schemes was numerically examined. Both the same-time-step and the multiple-time-step schemes were considered. Results show that the multiple-time-step subgridding scheme is late-time unstable due to larger-than-unity eigenvalues. As to the same-time-step subgridding schemes, stability is related to the treatment of corner regions.
Author(s): S. Wang
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 314 KB

Title: Parallel ICCG Solvers for a Finite-Element Eddy-Current Analysis on Heterogeneous Parallel Computation Environment
Abstract: This paper investigates fast electromagnetic field analysis on parallel computers mutually integrated by means of Grid computing technology. To utilize the heterogeneous parallel computation environment, we introduce four parallelized ICCG solvers: the block ICCG, load-balanced block ICCG, algebraic block redblack ordering, and recursive reordering methods. These solvers are evaluated in a finite edge-element eddycurrent analysis on integrated parallel computers.
Author(s): T. Iwashita, M. Shimasaki, J. Lu
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 212 KB

Title: A New 3D Ray-Tracing Acceleration Technique for the Analysis of Propagation and Radiation in Complex Enviroments
Abstract: A new 3D ray-tracing technique, based on the Angular Z-Buffer algorithm, [1] to speed-up reflection calculations is presented. The technique can be applied to the analysis of propagation in urban or indoor environments, or to the computation of radiation of antennas on-board complex structures amongst other applications. The technique is used in combination with the Uniform Theory of Diffraction (UTD) and shows a large reduction in CPU-time.
Author(s): I. González, C. Delgado, F. Saez de Adana, O. Gutiérrez, M. F. Cátedra
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 422 KB

Title: On the Convergence Properties of the Multiple Sweep Method of Moments
Abstract: This paper investigates the convergence properties of the Multiple Sweep Method of Moments (MSMM), both analytically and numerically, and presents some numerical results for various 2D scattering geometries, such as a strip, a cylinder, and a rough surface with and without a target on it. The MSMM is an O(N2) iterative method for solving the large matrix equations which arise in the method of moments (MM) analysis of electrically large bodies. In the MSMM, the body is split into P sections and the currents on these sections are found in a recursive fashion. Although the MSMM is a frequency domain solution, it has a time domain interpretation. The first sweep includes the dominant scattering mechanisms and each subsequent sweep includes higher order mechanisms. A connection between the MSMM and classical iterative methods is established in this paper. Under certain conditions, the MSMM is shown to be mathematically equivalent to a block Jacobi preconditioned system of equations that results from the moment method, and solved via the method of symmetric successive over-relaxation (SSOR) with relaxation factor ! = 1. Based on this connection, the convergence is analyzed by examining the eigenvalue distribution of the iteration matrix for different classes of 2D geometries, and for electric and magnetic field integral equation formulations and TEz and TMz polarizations. In addition, the MSMM is compared with other recently used iterative methods for rough surface scattering problems, namely the Method of Ordered Multiple Interactions (MOMI), or the Forward-Backward (FB) Method. The results show that the MSMM converges for some problems for which the MOMI (and FB) fails to converge, e.g., the rough surface with a target on it, or when the surface becomes multi-valued which causes large offdiagonal elements in the interaction matrix.
Author(s): D. Colak, R. J. Burkholder , E. H. Newman
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 340 KB

Title: Semi-analytical Approach to Sensitivity Analysis of Lossy Inhomogeneous Structures
Abstract: We propose an adjoint-variable technique for sensitivity analysis with structured-grid EM solvers, which can handle lossy inhomogeneous materials. In previous discrete adjoint-based approaches, the response derivatives with respect to shape parameters require the solution of a perturbed geometry, which has to be approximated. Here, we improve the algorithm by proposing a semi-analytical sensitivity formula where the system matrix derivatives consist of an analytical and a finite-difference term. It allows the use of the solution of the unperturbed structure with no approximation, which improves the accuracy. Applications are based on a frequency-domain solver based on the transmission line method.
Author(s): Shirook M. Ali, Natalia K. Nikolova, Mohamed H. Bakr
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 361 KB

Title: Model-Based Parameter Estimation (MBPE) for Metallic Photonic Crystal Filters
Abstract: An efficient method for the accurate computation of the response of photonic crystal filters is obtained when Model-Based Parameter Estimation (MBPE) is combined with accurate field solvers. In this paper, MBPE is combined with Multiple Multipole Program (MMP) and the Method of Auxiliary Sources (MAS) and the results are compared with results obtained from a commercial field solver. When metals are present in photonic crystal filters, strong material dispersion at optical frequencies cause nonlinearity of the filter response. It is demonstrated that MBPE is still useful although it is originally designed for linear systems.
Author(s): K. Tavzarashvili, Ch. Hafner, C. Xudong, R. Vahldieck, D. Karkashadze , G. Ghvedashvili
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 417 KB

Title: Scattering by PEMC (Perfect Electromagnetic Conductor) Spheres using Surface Integral Equation Approach
Abstract: This article discusses bistatic scattering by totally reflecting spheres. The spheres are either perfect electric, magnetic, or electromagnetic conductors (PEMC). The PEMC medium is described by the parameterM with special cases of PMC (vanishing M) and PEC (infinite M). The scattering by a small sphere of such a material from incoming plane wave can be explained by the interplay of electric and magnetic dipoles. The special characteristics of the radiation of PEMC spherers (different from PEC and PMC) include cross-polarization which is especially marked in the backscattering direction. The radiation pattern is rotated by an angle that has a simple connection with the M parameter. Scattering patterns of PEMC spheres with size parameters up to ka = 3 are shown and they also display cross-polarized properties. The computations are based on a MoM software to solve the surface integral equation for the fields.
Author(s): A. Sihvola , P. Yla-Oijala, I. V. Lindell
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 5431 KB

Title: Fast Frequency Sweep Scattering Analysis for Multiple PEC Objects
Abstract: The best polynomial approximation, performed by Chebyshev approximation, is applied to the scattering analysis of multiple arbitrary shaped perfectly electric conducting objects over a broad frequency band. For a given frequency band, the frequency points corresponding to the Chebyshev nodes are found by transformation of coordinates, and the surface electric currents at these points are computed by the method of moments. The surface current is represented by a polynomial function via the Chebyshev approximation, and the electric current distribution can be obtained at any frequency point within the given frequency band. Numerical examples show that the results generated by the presented approach agree to that provided by the method of moments at each of the frequency points, but the CPU time of the presented approach is reduced obviously without sacrificing much memory.
Author(s): C. Mingsheng, W. Xianliang, S. Wei, H. Zhixiang
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 299 KB

Title: RCS Computation of Targets Using Three Dimensional Scalar Parabolic Equation
Abstract: The parabolic equation (PE) method gives accurate results in calculation of scattering from objects with dimensions ranging from one to tens of wavelengths. Solving parabolic equation with the marching method needs limited computer storage even for scattering calculations of large targets. In this paper, the calculation procedure of radar cross section using scalar three dimensional parabolic equations is considered and the necessary equations are derived. In order to show the capabilities of the method two structures are analyzed. First scattered fields and RCS of an airplane in the forward direction are computed. Next, scattered fields and RCS of a reflector antenna in the backward direction are calculated. The obtained results are compared with physical optics results.
Author(s): A. R. Mallahzadeh, J. Rashed-Mohassel, M. Soleimani
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 697 KB

Title: Application of Quasi-static Method of Moments for the Design of Microwave Integrated Circuits and Antennas
Abstract: With the recent advancements in computer-aided design (CAD) technology, circuit simulators are being capable of simulating complex designs in a reasonably short time. To reduce the design cycle and development costs, design simulation is becoming a necessity for today’s microwave and millimeter wave (mmW) integrated circuit (IC) designs. Besides operating at microwave and mmW frequencies, those designs are fairly complex. Accurate prediction of circuit performance before fabrication becomes a must for shortening design cycles and for lowering engineering cost.
Author(s): C. P. Huang, S. Hammadi, J. Sercu, J. Bao, S. Kuran
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 537 KB

Title: New Heating Characteristics of a Radio Frequency Rectangular Resonant Cavity Applicator Using Various Antennas for Hyperthermic Treatment
Abstract: The heating characteristics of a radio frequency rectangular resonant cavity applicator excited by various antennas are investigated for use in hyperthermic treatment. The coupled electromagnetic and heat-transfer equations are solved to obtain the heating characteristics. Two types of antennas and three types of dielectric phantoms are used in the calculations and measurements. Clear differences in the heating characteristics are observed for these phantoms and antennas. Previously, we were only able to heat up the surface or end regions of the phantom, while it is now possible to uniformly heat up the deeper regions with the current applicator. Therefore, this applicator is suitable for hyperthermic treatment.
Author(s): Y. Tange, Y. Kanai , Y. Saitoh, T. Kashiwa
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 798 KB

Title: RF Coil Design for MRI Using a Genetic Algorithm
Abstract: In this work a Genetic Algorithm (GA) was used to optimize single and dual array Radio Frequency (RF) coils for imaging vasculature structures using Magnetic Resonance Imaging. Quasi-static equations were used to simulate sample noise and signal sensitivity profiles of the coil elements. Coil to sample and coil to coil interactions were taken into account, and the relative signal-to-noise ratio in the structure of interest was used as the cost function for the GA optimization.
Author(s): J. R. Hadley, C. M. Furse, D. Parker
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 291 KB

Title: Modeling of Ground-Penetrating Radar for Detecting Buried Objects in Dispersive Soils
Abstract: The detection of buried targets with groundpenetrating radars (GPRs) has been an issue of considerable attention during the last decades. In this paper, an efficient three-dimensional (3-D) time-domain numerical method is proposed for the simulation of GPR on dispersive soils. The soil is considered as an M-th order Debye medium with additional static conductivity and an unsplit-field perfectly matched layer (PML) is also presented to terminate such media. The radar unit is modeled with two transmitters and one receiver in order to eliminate undesired signals. The impact of radar frequency, soil parameters and object depth upon the ability to detect buried targets is investigated through several finite-difference time-domain (FDTD) simulations. The detection of multiple dielectric and conducting buried objects in stratified and inhomogeneous soils can be feasible through the tracing of the received energy of B-scan measurements in perpendicular linear paths.
Author(s): K. P. Prokopidis, T. D. Tsiboukis
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 911 KB

Title: Inverse Scattering of Inhomogeneous Dielectric Cylinders Buried in a Slab Medium by TE Wave Illumination
Abstract: The inverse scattering of inhomogeneous dielectric cylinders buried in a slab medium by transverse electric (TE) wave illumination is investigated. Dielectric cylinders of unknown permittivities are buried in second space and scattered a group of unrelated waves incident from first space where the scattered field is recorded. By proper arrangement of the various unrelated incident fields, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results are given to demonstrate the capability of the inverse algorithm. Good reconstruction is obtained even in the presence of additive Gaussian random noise in measured data. In addition, the effect of noise on the reconstruction result is also investigated.
Author(s): C. H. Huang, C. C. Chiu, C. J. Lin, Y. F. Chen
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 353 KB

Title: A Wavefront Launching Model for Predicting Channel Impulse Response
Abstract: Maintaining the topology of an expanding wavefront surface allows for a simpler time-domain wave ray launching model that is free from the problems associated with ray catching. In addition to the usual ray location and direction information, the wavefront launching model stores which rays are adjacent in the advancing wavefront surface. The added information allows interpolation over this surface, so the model easily incorporates diffracted waves and power density changes from beam spreading.
Author(s): M. Robinson
File Type: Journal Paper
Issue:Volume: 22      Number: 2      Year: 2007
Download Link:Click here to download PDF     File Size: 248 KB