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An exact treatment using the boundary value method for solving the problem of scattering of a line source field or a plane wave by a perfectly conducting elliptic cylinder coated by a confocal dielectric elliptical shell is presented. For the line source excitation the total field is calculated, while for the plane wave excitation the echo width is obtained. Sample and interesting results for the...
An approximate numerical method is developed to determine the electromagnetic wave scattering by imperfectly conducting objects located inside a lossy ground. The incident field of the exciting loop, which is located above the ground, is determined using the dyadic Green's functions for a half-space. The scattering problem is then formulated using the magnetic field integral equation of an unbounded...
Accurate eigenvalues of nonzero-integer spherical wave functions of coaxial and biconical structures are determined for both TE and TM fields. It is found that the number of the eigenvalues is equal to the order of the characteristic equations, i.e., the order of the related associated Legendre functions and their derivatives. For each TE mode there is a unique nontrivial eigenvalue, which is the...
The use of an edge condition in scattering problems is investigated. Various numerical schemes such as conformal transformation, Fourier expansion, and Fourier expansion with edge correction are examined. The developed numerical methods are then applied to investigate the dynamic range of each techniques and their validity.
We consider the electromagnetic fields which can exist in the presence of two perfectly conducting spheres in free space in the absence of external sources, i.e. the free oscillations. An asymptotic analytical solution for the natural frequencies and natural modes is presented, which is exact in the limit of infinite sphere separation. To our knowledge this is the first analytical treatment of the...
Lattice Gas Automata (LGA) can be considered as an alternative to the conventional differential equation description of problems in electromagnetics. LGAs are discrete dynamical systems that are based on a microscopic model of the physics being simulated. The basic constituents of an LGA are discrete cells. These cells are interconnected according to certain symmetric requirements to form an extremely...
This paper presents the generalization of the Ludwig-3 definition of linear co-polarization and cross-polarization. We say that our definition is a generalization because our definition agrees with the Ludwig-3 definition on boresight but departs further from the Ludwig-3 definition as the observation angle θ departs from zero as a result of the presence of a cos(θ) term in the generalized definition...
The general problem of coupling through apertures has applications in slotted arrays, directional couplers, microstrip lines, etc. Numerous references are available in the literature, most of which use the Green's theorem to reduce the problem to an integral equation for the unknown tangential electric field in the aperture. Of these, the moment method is especially attractive because it inherently...
In this paper the 2D and 3D scattering problems are investigated. It is shown that only for special cases; these two methods provide the same unique answer. The level of error for other cases is investigated. In MI, both plane wave and infinite line sources are important. In this paper the line source excitation is considered. The results and the detailed proof will be provided during the presentation...
A parametric study of a wide-band Vivaldi antenna is presented. Four models were simulated using a finite element method design and analysis package Ansoft HFSS v 10.1. The simulated return loss and realized gain of each model for a frequency range of 12 to 20 GHz is studied. The location of the phase centre, represented as the distance d (in cm) from the bottom of the antenna, with respect to which...
This paper presents the fundamental concept of wave propagation in periodic multilayer films consisting of two different materials, so-called one-dimensional electromagnetic bandgap (EBG) materials. To this end, Floquet's theorem is first presented. Next, the transmission-line analogy is used to simplify the concept of wave propagation in one dimension. The Bloch impedance concept is then presented,...
Lattice Gas Automata (LGA) can be considered as an alternative to the conventional differential equation description of problems in electromagnetics. LGAs are discrete dynamical systems that are based on a microscopic model of the physics being simulated. The basic constituents of an LGA are discrete cells. These cells are interconnected according to certain symmetric requirements to form an extremely...
Numerical solutions for electromagnetic integral equations describing scattering from electrically large complex objects continues to be a challenging problem. The classical method of moments (MoM) reduces the integral equations to matrix equations and produces dense linear systems. Since direct solvers for dense systems are impractical for large matrices, iterative methods are usually used. Among...
In recent years, considerable attentions have ban paid to time domain methods. The major part of these efforts have concentrated on applying Yee's (FD-TD), John's (TLM) or Begeron's algorithm to different structures. Nevertheless, the signal processing techniques for converting the resulting time domain data to frequency domain have been restricted to the DFT, FFT and Prony's methods. In this article...
In this paper, the wire grid modeling technique is compared with subdomain basis functions using a point matching technique. The comparison for two dimensional case is carried out in the paper and that for three dimensional case will be given during the presentation. It is found that the wire grid modeling technique is an approximate model for the point matching technique with subdomain basis functions...
A uniformly illuminated circular aperture is considered and the radiation pattern is computed using the aperture field integration method. For the integration algorithms three different methods of FFT, Simpson's rule and the Guass-Legendre are used. To compare the accuracy of these different techniques, the same integration is also performed analytically. It is shown that the Guass-Legendre technique...
General integral equations for quasistationary electromagnetic fields have been derived and an improved surface impedance model for conducting objects has been proposed. These equations have a simple structure and the amount of computation for their solution is substantially reduced with respect to that corresponding to the general electromagnetic field integral equations. The proposed modelling technique...
Simplified theory and its numerical computation are presented for the inclusion of the mutual coupling in the planar array theory of microstrip antennas of the circular disc patch type or the rectangular patch type. Although more rigorous treatments may be developed in the future or extended to other shapes, the purpose of the present task is to seek the most compact and simplified approach that still...
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