ISSN:0920-5071    

DOI:10.1163/156939389X00304

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Trade-off's between integral and differential equation formulations for electromagnetic wave scattering from highly inhomogeneous dielectric bodies are evaluated, via a comparison of three different frequency-domain formulations for TE-wave scattering from dielectric cylinders. The formulations considered include a volume integral equation, a volume differential equation combined with an approximate near-field radiation condition, and a hybrid method using both a surface integral and volume differential equation. Numerical results indicate that all three methods have similar accuracy for a given scatterer model, and that the methods incorporating differential equations have significant computational advantages over volume integral formulations.

ISSN:0920-5071    

DOI:10.1163/156939389X00313

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A finite-difference, frequency-domain (FD-FD) approach to electromagnetic wave scattering is presented. This approach evolved from recent progress that features the concept of generalized scattering amplitudes, the application of boundary-fitted curvilinear coordinate systems, and the use of Debye potentials for 3-D obstacle scatterings. The introduction of the radially non-oscillatory generalized scattering amplitudes circumvents the difficulties in dealing with oscillatory field quantities in the infinite exterior scattering region and allows the finite-difference method to be applied to scattering problems in an effective manner. The radiation condition in terms of the generalized scattering amplitude is very simple in form and can be enforced exactly in the far field. For a 3-D scattering problem the formulation in terms of Debye potentials, expressed as functions of body-fitted coordinates, not only decouples the vector scattering problem into a combination of two independent scalar scattering problems but also makes the exact enforcement of obstacle surface condition simple. Specific examples with numerical results validated by the eigenfunction expansion method and the moment method are given to illustrate the salient features of the FD-FD approach.

ISSN:0920-5071    

DOI:10.1163/156939389X00322

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A finite element based electromagnetic scattering program is used to identify the complex natural resonances for axisymmetric dielectric bodies. These resonances are found by way of a complex frequency s-plane search for the zeroes of the determinant of the global system matrix which represents the scattering solution. Examination of the behavior of the elements of this matrix also reveals the mode type, either TE or TM, the meridional order and the azimuth index. Computational examples are presented for the cases of a penetrable sphere, a 2:1 prolate spheroid and a 1:1 finite right circular cylinder, each composed of high density lossless dielectric.

ISSN:0920-5071    

DOI:10.1163/156939389X00331

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper describes the use of the conjugate gradient method in conjunction with the finite difference method for the calculation of the propagation characteristics of TE and TM modes, including cutoff wavenumbers and field distribution, of hollow conducting waveguides of arbitrary cross sections. This method is quite fast and accurate and can be applied in a straightforward fashion for the analysis of both TE and TM modes in waveguides of arbitrary cross sections. In order to check the accuracy of this method, the new approach has been applied to compute the cutoff wavelength of a rectangular waveguide as analytical results are available for this problem. This method has also been applied to compute the first six TE and TM modes for L-shaped, single ridge, vaned rectangular, T-septate and rectangular coaxial waveguides. Comparison of accuracy is made whenever data is available. Since the conjugate gradient method is an iterative method, computer storage is 6N instead of N2for conventional matrix methods. Hence problems with a million unknowns can easily be solved on a VAX 11/785. As the conjugate gradient method directly solves the eigenvalue problem, the propagation characteristics can be obtained efficiently with an a priori specified degree of accuracy.

ISSN:0920-5071    

DOI:10.1163/156939389X00340

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Several error criteria have made the scientific scene for purposes of adaptive finite element mesh generation. However, it is demonstrated in this paper, that when applied to the same problem, they give very different meshes as iterations on the mesh proceed. A comparison of the various criteria is made and it is shown that different measures of error give better values of different physical quantities, such as energy, flux density and potential. The choice of error criterion, therefore, rather than being arbitrary, should be based on the design task at hand.

ISSN:0920-5071    

DOI:10.1163/156939389X00359

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939389X00368

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor