Detection of unresolved Rayleigh targets using adjacent bins

Abstract

Amplitude comparison monopulse systems provide angular localization of a target. When multiple targets in the illuminating beam occupy a single resolution cell, then the targets are unresolved. When knowledge of the presence of unresolved targets is known a-priori, then estimators derived in existing literature can be used for angle localization of the targets. However, the presence of unresolved targets is often not known a-priori, and in these cases typical single-target DOA estimators can fail. Detection of unresolved targets has been treated in existing literature for the case of a single range sample, ignoring range straddling. In recent literature, range and angle estimators exploiting range straddling show estimation performance enhancements in the single and multiple target cases. In those works, the correlation between adjacent bins, which is ignored in traditional radar literature, is used in the estimation of multiple targets. In this work, we expand upon recent literature by revisiting the topic of detection of unresolved targets with a signal model that includes range straddling. We use the generalized likelihood ratio test (GLRT) for the hypothesis test of multiple targets vs. a single target. A performance comparison with existing algorithms is provided. Results suggest that the proposed GLRT can provide significant benefits over existing approaches for the detection of unresolved targets.