摘要:

The problem of scattering by a coated elliptical conducting cylinder which extends infinitely long in the Z direction is analyzed when a plane electromagnetic wave is obliquely incident. The medium of the layer is assumed homogeneous and isotropic but lossy. Since the scattering object is an elliptical cylinder, the solutions of the wave equation are given in terms of radial and angular Mathieu functions. The analyses of the E-Wave and the H-Wave incidence cases are considered separately. The boundary conditions are applied at two surfaces to obtain the expansion coefficients of the scattered and transmitted waves. Bistatic radar cross sections, specular differential cross sections, and efficiency factors are determined with these coefficients.

ISSN:0920-5071    

DOI:10.1163/156939391X00770

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this paper, the radiation loss formula in bent planar waveguides with graded-index profile is given and some numerical results for the bending loss in bent step-index slab waveguides are shown and compared with other previous work.

ISSN:0920-5071    

DOI:10.1163/156939391X00789

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Double-parameter and single-parameter tuning of a digitally-tuned, electrically-short monopole antenna at the center of a circular groundplane are investigated to determine the range of groundplane radii for which the same tuning words can be utilized in maintaining a specified antenna gain over a given frequency band. It is found that the range of groundplane radii is generally not significantly larger with double-parameter tuning than with single-parameter tuning. It is concluded that it may not be possible to use the same tuning words for all groundplane radii of interest without a substantial loss in antenna gain because of mismatch loss at some frequencies, particularly at the low end of the band.

ISSN:0920-5071    

DOI:10.1163/156939391X00798

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The method of homogenization is applied to derive the boundary conditions for the average fields at a periodic metal grating of ribbon conductors. This method leads to a separate determination of the fine structured boundary layer fields and of the average fields which exist at a distance from the structure. Solution of these problems leads to boundary conditions for the average fields which have been referred to in the literature as "equivalent" or "averaged" boundary conditions. These conditions can be applied to the solution of the waveguide, scattering, and antenna problems involving electrically fine gratings.

ISSN:0920-5071    

DOI:10.1163/156939391X00806

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In electromagnetic boundary value problems integral equations involving the free space Green function for the Helmholtz equation often occur. Using the method of moments to numerically solve such an equation a matrix equation is obtained. The entries of the matrix are given as multidimensional integrals which in general have to be calculated numerically. This paper presents an efficient method to approximate the main part of these integrals. The free space Green function is expanded in scalar spherical wave functions. The translation properties of these wave functions then imply that the matrix elements can be expressed as a series of multipole moments. The method is illustrated by an implementation in the static case and the computation of the capacitance of a square plate. Basis functions with the correct edge and corner behaviour are used. The calculations of the multipole moments are done analytically. Numerical results using the point-matching and Galerkin's method are presented.

ISSN:0920-5071    

DOI:10.1163/156939391X00815

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A mode-matching method in the sense of least squares is proposed to analyze diffraction problems of thin-film waveguides with a rectangular groove structure of finite extent. Two diffraction problems are treated. The first problem is related to that of the grating coupler. The plane wave is incident on the surface of the core region from the cover region of the thin-film waveguide under the Bragg condition in the first problem. The second problem is related to those of the distributed feedback and Bragg reflection lasers. In the second problem, the lowest order guided mode is incident into the periodic part through the unperturbed part of the waveguide under the Bragg condition. The approximate scattered fields of each region of the waveguide are described by the superposition of plane waves with band-limited spectra. These approximate wave functions are determined by the minimization of the mean-square boundary residual. This method results in simultaneous integral equations of the Fredholm type of the second kind for these spectra. The results based on the first order approximate solutions of the integral equations are presented.

ISSN:0920-5071    

DOI:10.1163/156939391X00824

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

There is an increasing interest in the study of electronic and optical devices immersed in a layered dielectric surround. Modern fabrication techniques of solid-state chips have made possible high density integrated electronic and optical circuits. Advances in this technology have been on a revolutionary scale and have greatly exceeded corresponding advances in research which seeks to understand and predict device behavior. Obviously, the development of new and more effective methods of analysis is of paramount importance. An electric field integral equation is developed for the transverse field components within longitudinally-uniform integrated dielectric waveguides. Uncoupling of the axial component of the field from the transverse components reduces the number of scalar unknowns, thereby expediting numerical computation of approximate solutions. Furthermore, the resulting description is a pure integral equation as opposed to an integro-differential one. The dominant singularity of the Green's dyad is sufficiently weak to avoid necessitation of a principal value integral and the corresponding depolarizing dyad. Results from the application of this formulation are given, and compare favorably with established data.

ISSN:0920-5071    

DOI:10.1163/156939391X00833

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00842

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00851

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor