ISSN:0920-5071    

DOI:10.1163/156939392X00742

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A full Green's function approach is taken to formulate an infinite planar periodic structure, such as a phased array, with arbitrarily shaped elements. A reaction integral equation is then written and solved by the moment method with Galerkin weighting. The metallic surface of the array element is modelled by triangular surface patches similar to those of Rao, Wilton and Glisson [4]. This method is suitable for planar periodic structures, such as phased arrays or frequency selective surfaces, with unit cells that are of arbitrary 3-D shape and may contain induced currents perpendicular to the array plane. This general and versatile computer program has been extensively checked against data in the literature and with our measurements, and good agreements were observed.

ISSN:0920-5071    

DOI:10.1163/156939392X00751

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A novel absorbing boundary condition (ABC), to be used with finite difference and finite element electromagnetic radiation and scattering problems is described. It is based on anechoic chamber absorber foam geometry, with specified complex permittivity and permeability. The advantage of this absorbing boundary is that it prevents reflections from much wider incident angles than currently used lattice termination conditions. Since incident waves need not be normal to this boundary for absorption, the boundary can be placed much closer than previously possible. This new type of ABC can be used to absorb scattered waves in a local sense, so the electrical size of the scattering object does not effect the distance from it to the ABC. Since even a modest decrease in the required separation distance yields a huge savings in the number of required matrix elements for three dimensional geometries, this novel ABC may greatly improve the general applicability of computational electromagnetics.

ISSN:0920-5071    

DOI:10.1163/156939392X00760

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The numerical error associated with the simulation of linear wave phenomena using finite methods in both the frequency and time domain is considered. Both exact and numerically generated solutions of finite difference and finite element approximations to the scalar Helmholtz equation in one and two dimensions are used to demonstrate the dependence of the accuracy of the discrete solution on the number of nodes per wavelength, the electrical size of the computational domain, the order of the discretization, and the type of boundary conditions used. The results from these studies, as well as results from similar studies for finite difference approximations of Maxwell's equations in the time domain, are used to generate simple expressions for selecting the nodal density to maintain a desirable accuracy.

ISSN:0920-5071    

DOI:10.1163/156939392X00779

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper reports numerical solutions to three dimensional electromagnetic scattering problems. In particular low frequency scattering in a conductive medium is addressed. Numerical solutions of two simple problems are reported and compared with analytical results to evaluate the performance of the technique presented. The solution is carried out in the frequency domain by coupling a multipole expansion with a finite element solution. Numerical results are validated against analytical solutions. Excellent results are obtained for the test cases reported with numerical and analytical solutions agreeing to within 5%.

ISSN:0920-5071    

DOI:10.1163/156939392X00788

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The electromagnetic scattering from large curved ducts with complex terminations is studied here by a hybrid technique. The propagation of electromagnetic waves in the duct is analyzed in terms of an approximate modal solution. A finite-difference technique is employed for computing the reflection characteristics of the complex terminations. Numerical results are obtained for two-dimensional geometries.

ISSN:0920-5071    

DOI:10.1163/156939392X00797

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A hybrid combination of modal/ray-tracing and numerical techniques is developed for treating inhomogeneous or arbitrarily shaped terminations in ducts. The problem-domain, usually electrically large, is divided into two regions: one region is homogeneous and some distance away from the termination; the other one which includes the termination is (in general) inhomogeneous. A modal or ray-tracing solution is developed to solve the incoming wave in the first region, while the solution for the termination region is obtained numerically (finite differences) with an initial estimate of the boundary condition on the interface between the two regions. Then, an iterative technique, Boundary Relaxation Method (BRM), is utilized to implement the correct boundary condition. In this paper, some 2-D waveguide termination problems are analyzed to illustrate the BRM. Examples include the study of loaded waveguide cavities.

ISSN:0920-5071    

DOI:10.1163/156939392X00805

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939392X00814

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor