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Title: ELECTROMAGNETIC SCATTERING FROM RADIALLY OR AXIALLY INHOMOGENEOUS OBJECTS
Abstract: A computer program based on the method of moments approach is developed to compute electromagnetic scattering from axisymmetric objects. The object may consist of N linear isotropic homogeneous regions. These regions may be arranged axially and/or radially with the axis of symmetry. Surface integral equations (SIE) formulation, EAPMCHW, is used to formulate the problem. Other formulations can easily be incorporated in the computer code. Bistatic and monostatic Radar Cross Sections (RCS) for several benchmark geometries are computed. The computed results are verified by comparison with measured and exact calculated results. In some cases the self-consistency method is used to perform the verification. The measured and calculated data presented in this paper are expected to serve as benchmarks for other researchers in the field. [Vol. 7, No. 1, pp. 4-23 (1992)]
Author(s): Ahmed A. Kishk, Mohamed Abouzahra
File Type: Journal Paper
Issue:Volume: 7      Number: 1      Year: 1992
Download Link:Click here to download PDF     File Size: 719 KB

Title: APPLICATION OF EQUIVALENT EDGE CURRENTS TO CORRECT THE BACKSCATTERED PHYSICAL OPTICS FIELD OF FLAT PLATES
Abstract: In the microwave case the physical optics (PO) method is frequently used for the analysis of complex structures which are modeled by flat plates of triangular or quadrangular shape. The study of the radar cross section (RCS) of an isolated panel, however, reveals deviations from experimental results which are due to edge diffraction effects not considered by PO. In order to correct the PO-field by an additive field term, the equivalent fringe currents (EC) of Michaeli have been used to derive the backscattering matrix of an isolated edge. By adding the matrices of the individual edges to the PO-matrix the RCS of a square flat plate with zero and finite thickness is analysed and the result is compared with measurements. The efficiency of the method is demonstrated for objects modeled by a higher number of panels and edges, namely a cylinder and a double dihedral. All computations were performed with the computer code SIG5 of the Institute. [Vol. 7, No. 1, pp. 24-47 (1992)]
Author(s): V. Stein
File Type: Journal Paper
Issue:Volume: 7      Number: 1      Year: 1992
Download Link:Click here to download PDF     File Size: 1217 KB

Title: APPLICATION OF PARALLEL PROCESSING TO A SURFACE PATCH / WIRE JUNCTION EFIE CODE
Abstract: A surface patch / wire junction EFIE method of moment algorithm, JUNCTION, developed by the University of Houston has been implemented in a transputer based parallel processing environment installed in a personal computer. This paper addresses transputer hardware and software options, the JUNCTION algorithm, techniques for parallelizing matrix analysis algorithms, and performance results. The transputer array was found to provide a flexible, low-cost, high performance desktop computing environment for method of moment analysis. [Vol. 7, No. 1, pp. 48-66 (1992)]
Author(s): L. C. Russell, J. W. Rockway
File Type: Journal Paper
Issue:Volume: 7      Number: 1      Year: 1992
Download Link:Click here to download PDF     File Size: 1119 KB

Title: A RECURSIVE TECHNIQUE TO AVOID ARITHMETIC OVERFLOW AND UNDERFLOW WHEN COMPUTING SLOWLY CONVERGENT EIGENFUNCTION TYPE EXPANSION.
Abstract: Eigenfunction expansions for fields scattered by large structures are generally very slowly convergent. The summation often consists of two factors where one factor approaches zero and the other factor grows in magnitude without bound as the summation index increases. Each term of the expansion is bounded; however, due to the extreme magnitude of the individual factors, computational overflow and underflow errors can limit the number of terms that can be computed in the summation thereby forcing the summation to be terminated before it has converged. In this paper an exact technique that circumvents these problems is presented. An auxiliary function is introduced which is proportional to the original factor with its asymptotic behavior factored out. When these auxiliary functions are introduced into the summation, we are left with the task of numerically summing products of well behaved factors. A recursion relationship is developed for computing this auxiliary function. [Vol. 7, No. 1, pp. 67-77 (1992)]
Author(s): Gary A. Somers, Benedlkt A. Munk
File Type: Journal Paper
Issue:Volume: 7      Number: 1      Year: 1992
Download Link:Click here to download PDF     File Size: 508 KB

Title: 'H-ORIENTED' AND 'B-ORIENTED' METHODS IN A PROBLEM OF NONLINEAR MAGNETOSTATICS: SOME METHODOLOGICAL REMARKS
Abstract: Problems which depend on a small parameter in their formulation can often be studied by a perturbation approach. Whether the perturbation is "regular" or 'singular is important in many respects. In magnetostatics, due to some inherent duality, both kinds of perturbation may happen, depending on the chosen formulation ( 'b-oriented' vs. 'h-oriented' methods). Singularly perturbed problems are numerically more difficult than regularly perturbed ones . We suggest that this might explain why, as some recent numerical observations seem to suggest, b-oriented methods should give better accuracy in a specific class of nonlinear magnetostatic problems at high permeability. [Vol. 7, No. 1, pp. 78-89 (1992)]
Author(s): A. Bossavit
File Type: Journal Paper
Issue:Volume: 7      Number: 1      Year: 1992
Download Link:Click here to download PDF     File Size: 659 KB