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Title:Efficient Techniques for Near-Field Computation and Subreflector Analysis
Author(s):Rushdi, Ali Muhammad Ali
Department / Program:Electrical Engineering
Discipline:Electrical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Abstract:This thesis is divided into three main parts. In the first part a new technique for near-field computation is proposed. Integral representations of the radiating near field are obtained by making Fresnel approximations in the phase, magnitude and direction of the exact field expression. The analysis is general in the sense that neither the vectorial nature of the field nor the curvature of the antenna surface is neglected. Alternatively, the radiating near field is expressed via the Sommerfeld-Wilcox expansion. For field computation, the series method of the modified Jacobi polynomials is employed. Advantages of this method over other existing methods are shown, and details for implementing the method for both planar aperture and reflector antennas are given.
In the second part, the problem of reflection from smooth convex surfaces is considered. In certain applications involving this problem, the conventional geometrical optics (GO) solution is not sufficiently accurate. A generalization of the conventional GO is presented and closed-form expressions are derived. The derivation of this generalized geometrical optics (GGO) formula is based on the Fresnel transformation between two planes, one of which contains the specular point, while the other passes through the observation point. Subsequently, the GGO formular is compared with the transport equation of the higher-order GO. A modified GGO formular is shown to yield the field correct to the order (1/k) in the case of reflection from a parabolic cylinder or a paraboloid of revolution.
In part three, an efficient technique for computing the reflected field from a smooth numerically specified surface is developed. Both surface interpolation and search for the specular point are bypassed. Basically, the method starts by computing the reflected rays off the surface at the numerically specified points. Next, the observation point is associated with the pencil composed of the reflected rays nearest to it. Finally, the field is computed via the GO or the more accurate GGO formula. The method was applied to a test problem. Time and accuracy comparisons with the conventional method are presented.
Issue Date:1980
Description:149 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
Other Identifier(s):(UMI)AAI8026583
Date Available in IDEALS:2014-12-12
Date Deposited:1980

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