Distributed Target Detectors With Capabilities of Mismatched Subspace Signal Rejection

Abstract

In this paper, we consider the problem of distributed target detection with subspace signal mismatch. Precisely, the echoes reflected by the distributed target all come from the same direction, and the signal steering vector is assumed to lie in a preassigned subspace. However, the actual signal steering vector does not completely belong to the presumed subspace, resulting in subspace signal mismatch. We focus on the design of selective detectors, which have good capabilities of mismatched signal rejection. To this end, we add a fictitious signal under the null hypothesis, which is orthogonal to the nominal signal subspace in the whitened or quasi-whitened subspace. According to the generalized likelihood ratio test criterion, we devise two effective detectors. Compared with the existing ones, the proposed detectors exhibit improved selectivity capabilities for signal mismatch at the price of a little bit performance loss in the case of no signal mismatch. Moreover, for the case of point-like target, which is a special case of distributed target, we derive analytical expressions for the probabilities of detection and false alarm. Simulation results illustrate the superiority of the proposed detectors and confirm our theoretical results.