Passive Radar STAP detection and DoA estimation under antenna calibration errors

This paper addresses the problem of clutter cancellation for slowly moving target detection and localization in multichannel passive radar onboard mobile platforms. A post-Doppler space-time adaptive processing (STAP) approach is exploited, in the case of an angle-dependent imbalance affecting the receiving channels.While clutter suppression capability is ensured by the adaptivity of space-time filtering, different solutions are compared, aimed at recovering the detection performance losses associated to channel calibration errors. A space-time generalized likelihood ratio test (GLRT) scheme is considered, where the steering vector is not specified in the spatial domain, resulting in a non-coherent integration of target echoes across the receiving channels. This is compared with a fully coherent GLRT scheme where echoes from stationary scene are exploited for proper calibration of spatial steering vector mismatch. The first scheme proves to be a simple solution for target detection in the passive radar case, offering comparable clutter cancellation capability. The second scheme, at the expense of an additional stage, offers slightly better detection performance and preserves target direction-of-arrival (DoA) estimation capability. Finally, the STAP scheme is employed for maximum likelihood (ML) estimation of target DoA, evaluating the role of the steering vector calibration against the negative impact of channel imbalance. The effectiveness of the proposed approaches is tested against both simulated and experimental data from a DVB-T based mobile passive radar.