Title

Effects of mutual coupling on the direction-finding performance of a linear array in a multiple-source environment using the method of moments

Date of Award

1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical Engineering and Computer Science

Advisor(s)

A. T. Adams

Second Advisor

Tapan K. Sarkar

Keywords

Arrays, Mutual coupling

Subject Categories

Electrical and Computer Engineering

Abstract

Modeling an array as a collection of uniformly-positioned identical dipoles and signals as coherent and nonrandom narrowband plane waves, the method of moments is used to study the effects of mutual coupling on the direction-finding performance of the forward-backward linear prediction (FBLP) method.

Computer simulations show that when the sensor outputs which contain the effects of mutual coupling are used for processing, the technique is incapable of obtaining the directions of arrival (DOA) with satisfactory accuracy. Thereupon, Galerkin's method is applied to compute the matrix that characterizes the mutual coupling among the dipoles. By using this matrix, the outputs which would exist if mutual coupling were absent are then extracted from the sensor outputs for processing. It is shown that a dramatic difference in the performance of FBLP is thus achieved.

Due to some errors in the dipole model used in computing the matrix, slight discrepancies appear between the mutual coupling characterized by the matrix and that actually occurring among the dipoles. These in turn lead to the occurrence of errors in the computed outputs and yet a quite realistic emulation of real situations.

Two methods are devised for finding the number of sources; one makes use of Weyl's theorem and the other, variations of a prediction parameter with prediction order. A method of finding the DOA using Prony's method and refining them using averaging is also devised. The results of these methods are examined and appear to be satisfactory.

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