Performance analysis of diversely polarized antenna arrays

The performance of direction finding systems utilizing diversely polarized antenna arrays is investigated. The Cramer-Rao bound (CRB) is used to evaluate the accuracy of the estimated directions of arrival. The resolving power of the array is evaluated by analyzing the performance of a likelihood ratio detector designed to determine whether the signals observed by the array originate from a single source or from two closely spaced sources. Numerical examples and analysis of some special cases provide insights into the improvement in direction finding accuracy and in the resolving power of the array due to polarization diversity. The case of a signal in the presence of an interferer is studied in some detail. The CRB and the probability of detection are evaluated as functions of the spatial separation and the polarization difference between signal and interferer, signal-to-noise ratio, and signal-to-interference ratio. Performance comparisons are made between uniformly polarized and diversity polarized arrays. It is shown that improved direction finding performance can be obtained by using polarization diversity, with no increase in hardware complexity