摘要:

The electromagnetic plane wave scattering by oblate spheroidal raindrops is investigated in this paper using the full-wave eigen-expansion in terms of the spheroidal vector wave functions so as to obtain an exact solution of the total (or extinction) cross section of the spheroidal raindrops. In this analysis, both TE- and TM-mode incident plane waves (or parallel and perpendicular polarizations) are considered. As the permittivity of the raindrop water is a function of both the operating frequency and the outdoor temperature, the Ray's program is utilized to compute the lossy raindrop permittivity. A Mathematica program is developed based on the computation of the radial and angular spheroidal wave functions with complex arguments. Comparison between the spheroidal wave function values computed using this algorithm and the available data in the literature shows that the algorithm developed here has a better accuracy. Also, the total cross sections of the raindrops obtained using the full-wave oblate spheroidal eigenfunctions are compared with those using the T-Matrix approach; and a very good agreement between them is found.

ISSN:0920-5071    

DOI:10.1163/156939398X00962

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Scattering from a time-harmonic wave normally incident upon an inhomogeneous dielectric slab is considered. Based on the use of two Riccati equations derived from two different modeling procedures, an approximation to the unknown permittivity profile is derived. The approximation scheme is based upon constructing the Nthdegree interpolation polynomial to approximate the reflection coefficient and the permittivity profile using Legendre-Gauss-Lobatto collocation points. An example is given to demonstrate the accuracy of the developed scheme.

ISSN:0920-5071    

DOI:10.1163/156939398X00971

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A full wave analysis of the aperture coupled microstrip patch antenna using a Mixed Potential Integral Equation (MPIE) approach is proposed. The problem is formulated as three coupled integral equations where the unknowns are the electric surface currents on the patch and feedline and the magnetic surface current on the aperture. Method of Moments (MOM) is then applied to solve for the various current distributions. With the sole use of closed-form Green's functions, integration in the spectral domain or Sommerfeld integral is completely avoided. The technique results in a very efficient algorithm whose computational speed is generally superior to that of spectral domain approach.

ISSN:0920-5071    

DOI:10.1163/156939398X00980

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper, we investigate the problem of a cylindrical Gaussian beam incident perpendicular on an infinitely long multilayered cylinder. The incident Gaussian beam (TEM00) is expanded in terms of plane wave spectrum and vector cylindrical harmonics. The theory of the interaction between a 2D Gaussian beam and an infinite multilayered cylinder is presented. The electric and magnetic fields bases on the Helmholtz equation in circular coordinates are derived. The modified algorithm for beam shape coefficient Cnand a new recursive formulae as well as the computing procedure to calculate the scattering coefficients anIIand bnIfor TE and TM modes are proposed. The stability of the numerical scheme allows to increase by several magnitude orders of the computational domain, both in size parameter and in the number of layers for a given size. Numerical results including scattering fields and scattering width are given for several kinds of cylinders.

ISSN:0920-5071    

DOI:10.1163/156939398X00999

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We show in this paper that the velocity of a charged particle cannot be taken as an independent variable as done in Euler-Lagrange calculation if we take into account the relativistic behaviour of the particle.

ISSN:0920-5071    

DOI:10.1163/156939398X01006

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents a full-wave analysis of cross polarization and transmission loss effects caused by a dielectric hemi-spherical radome and rainfall. The radome covered by a rain-water layer is centre-placed on an aperture on the ground plane and excited by the dominant TE 11 circular waveguide. The dyadic Green's function (DGF) technique that serves as a full-wave analysis is applied in the analysis, instead of the conventional analytical techniques. Numerical computations with excellent accuracy and fast convergence are carried out by using Mathematica package to demonstrate the effects of the radome with a rain-water layer on the far-field power pattern, cross polarization and total transmission loss. It is shown that the antenna radiation performance such as antenna pattern, transmission loss, and cross polarization becomes severely affected when the thickness of the dielectric radome is selected improperly, and is further degraded when rain water accumulates on the dielectric radome.

ISSN:0920-5071    

DOI:10.1163/156939398X01015

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Three types of adaptive multiscale moment methods are presented here for analyzing electromagnetic scattering from perfectly conducting two-dimensional electrically large objects. The conducting structures are assumed to be in a free-space medium and is illuminated by a TM plane wave. The three algorithms decompose the conventional method of moment matrix into a scaled-block matrix through a matrix multiplication. The numbers of unknowns corresponding to the linear equations at increasing scales can be automatically reduced by using a suitable threshold and the solution obtained from previous scales. Numerical results for the monostatic as well as bistatic radar cross section of several electrically large objects are presented. Comparison has been made with respect to the numerical solution obtained by the moment method. The objective of this paper is to illustrate that a possibility exist for efficiently reducing the size of the linear equations in an automatic fashion utilizing the adaptive multiscale moment methods.

ISSN:0920-5071    

DOI:10.1163/156939398X01024

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The transient behaviour of the resistively loaded wire antenna radiating in the presence of a lossy half-space is analyzed in the time domain. The mathematical model is based on a corresponding time domain Hallen integral equation. The influence of a lossy half-space is taken into account via the Fresnel space-time reflection coefficient appearing in the integral equation kernel. The resulting integral equation is then solved by the space-time finite element procedure. Numerical results for the current distribution along the wire are obtained for the case of dielectric half-space.

ISSN:0920-5071    

DOI:10.1163/156939398X01033

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We present here a systematic investigation of dielectric waveguide loaded with a metal-strip grating which is realistically characterized by a complex dielectric constant with a negative imaginary part to account for the finite conductivity of the metal strips. The method of mode matching is employed to solve such a boundary-value problem, and the effects of the structure parameters on the dispersion characteristics are critically examined, with a particular attention directed toward the attenuation constant due to the Bragg reflection, radiation and absorption of the grating waveguide.

ISSN:0920-5071    

DOI:10.1163/156939398X01042

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The diffraction of plane electromagnetic waves by three parallel thick impedance half-planes is investigated rigorously by using the Fourier transform technique in conjunction with the mode matching method. This mixed method of formulation gives rise to two scalar modified Wiener-Hopf equations of the second kind for odd and even excitations respectively. The solution of each Wiener-Hopf equation contains a set of infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the plate impedances, plate thickness and the distance between the plates, wherefrom the effect of these parameters on the diffraction phenomenon is studied.

ISSN:0920-5071    

DOI:10.1163/156939398X01051

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor