摘要:

Analysis of arbitrarily shaped three-dimensional (3D) objects in a multilayered medium using the method of moments (MoM) requires the computation of the Green's functions. When MoM is applied in the spatial domain, a 3D integral (one for the Sommerfeld integral, the other two for the integral over the source triangle) should be evaluated. The evaluation of the Sommerfeld integrals is a time-consuming process. A commonly encountered solution for this problem is to perform interpolations using preestablished look-up tables. Here, a general 3D interpolation model has been developed. The interpolation scheme is to select M vertical planes (perpendicular to the interfaces of the multilayered medium) to be tabulated in an overlapping manner to interpolate between them. In this scheme, all the grid values on the same vertical plane are tabulated and a single subroutine call is required to evaluate the Green's function. The interpolation model has been employed to calculate the current distributions on a TE01delta-mode dielectric resonator excited with a microstrip line.

ISSN:0272-6343    

DOI:10.1080/027263400308357

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A recent result showed that guided transverse electromagnetic (TEM) waves of a very general form could be propagated in an inhomogeneous isotropic dielectric medium with permittivity proportional to Psi-2, where Psi is the cylindrical radius in the usual (Psi,phi,z) cylindrical coordinate system. This has the important property that the permeability mu can be taken as mu0, a constant. Moreover, very general conductor cross sections in (z ,Psi)coordinates can be specified. This allows for the construction of dispersionless bends in high-voltage transmission systems in which the pulse rise time is small compared to transit times across the transmission-line (e.g., coax) cross section. This is important for high-power pulse sources and antennas. The analysis shows that while the permeability can be allowed to be variable, the choice of mu=mu0allows one to specify purely dielectric lenses. Thus the generalized form of a TEM plane wave involving inhomogeneous constitutive parameters can be used for generating lens designs based on the scaling.

ISSN:0272-6343    

DOI:10.1080/027263400308366

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A surface impedance boundary condition (SIBC) is presented for the finite-difference time-domain (FDTD) simulation of surface-emitting lasers with Bragg stacks. This method eliminates the need to directly implement the actual Bragg stack structure in the FDTD code and enables three-dimensional FDTD modeling of surface emitting lasers such as vertical cavity surface-emitting lasers (VCSELs). The SIBC is derived from the equivalent surface impedance properties at the interface between the cavity and Bragg stack. The three-dimensional finite-difference formula tions of the SIBC are given in this paper. Simulations of VCSELs are performed with both the SIBC and the actual Bragg stack structure. The excellent agreement obtained between these two simulations shows the validity of the SIBC developed in this work.

ISSN:0272-6343    

DOI:10.1080/027263400308375

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Plane-wave propagation is studied in the most general bianisotropic medium in which the electromagnetic wave can be split into two eigenwaves with certain polarizations depending on two arbitrary directions in space. Hence the whole problem splits into two parts. The dispersion dyadics of the materials seen by the eigenwaves are derived and the refractive indices are solved for arbitrary direction of propagation. Also, a general expression for the eigenpolarizations is found. The theory is applied to some cases fitting the requirements of the media.

ISSN:0272-6343    

DOI:10.1080/027263400308384

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The etalon boundary-value problem technique for approximately solving three-dimensional diffraction problems has been suggested. On etalon boundary-value problems, we use two-dimensional problems which are capable of exact solutions (for example, by the Wiener-Hopf technique). The field sought along one of the coordinate axes is taken to be locally coincident with that in the corresponding etalon problem. The amplitude coefficient (constant for the etalon problem) is assumed to be varying and is determined by substituting the above-mentioned solution representation into wave equations. Applications of the approach developed for the problem of electromagnetic-wave coastal refraction for a coast with a curved (random) coastal line and for the problem of wave diffraction by a perfectly conducting half-plane with a curvilinear edge have been considered.

ISSN:0272-6343    

DOI:10.1080/027263400308393

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Effects of double helical conductances of surfaces (HCSs)on the multiple scattering of an eccentrically two-layered bianisotropic cylinder array are investigated. The mathematical treatment is based on the mode matching approach combined with the addition theorem for cylindrical wave function. In the analysis, the obliquely incident wave is assumed to be a TEz-polarization. Numerical examples are presented to show the effects of the variations of the twist angles on the co- and cross-polarized bistatic echo widths for a bianisotropic four-cylinder array, and the special cases of the T- and L-strips are also considered. It is numerically demon strated that for the double HCSs, a very strong resonant scattering can be expected under certain circumstances, and such a resonant scattering can be suppressed by introducing T- or L-strips at the inner surface of the inhomogeneous (bi)anisotropic cylinders.

ISSN:0272-6343    

DOI:10.1080/027263400308401

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor