Analysis of a signal estimation algorithm for diversely polarized arrays

The problem of separating and estimating the waveforms of superimposed signals received by a diversely polarized array is considered. Signal estimation is accomplished by a two-step procedure: (1) The directions of arrival and polarization parameters of all the signals are estimated using an eigenstructure-based technique; (2) The estimated signal is obtained as a linear combination of the array outputs, with weights that are computed from the estimated direction/polarization parameters. The objective is to analyze the quality of the estimated signal in terms of the output signal-to-interference ratio (SIR) and output signal-to-noise ratio (SNR). Closed-form expressions are derived for the output SIR and SNR of a general diversely polarized array. By evaluating these expressions for selected test cases it is shown that polarization sensitive arrays can provide significantly higher output SIR and SNR than uniformly polarized arrays. The performance improvement is especially significant for closely spaced sources with sufficiently different polarization characteristics