Abstract
This article addresses the problem of clutter cancelation 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 the clutter suppression capability is ensured by the adaptivity of space-time filtering, different solutions are compared, aimed at recovering the detection performance losses associated with 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 noncoherent integration of target echoes across the receiving channels. This is compared with a fully coherent GLRT scheme where echoes from the stationary scene are exploited for the 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 cancelation 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 the maximum-likelihood 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.
Highlights
Over the past few years, renewed and increasing attention has been devoted by the scientific community to the passive radar technology
We have shown how the presence of an unknown imbalance affecting the receiving channels can impact on moving target detection performance of a mobile passive radar
We propose two possible strategies for target detection, aimed at recovering the performance losses associated with channel calibration errors in a mobile passive radar exploiting a space-time adaptive processing (STAP) scheme
Summary
Over the past few years, renewed and increasing attention has been devoted by the scientific community to the passive radar technology. We point out the fundamental role of a postDoppler STAP approach in preserving clutter cancelation capability, in the presence of channel calibration errors, identifying it as suitable for mobile passive radar It takes the advantage of the long integration time and the resulting fine Doppler resolution to considerably reduce the size of the adaptive problem and intrinsically compensate for the angle-dependent channel errors by operating on a clutter subspace accounting for a limited angular sector. Such capability requires the availability of multiple spatial degrees of freedom, which must be properly exploited both for space-time clutter filtering and for target DoA estimation, and it can be severely compromised by the presence of channel imbalance To this purpose, the proposed STAP scheme is adopted for a maximum-likelihood (ML) DoA estimation, assessing the key role of the steering vector calibration in mitigating the negative impact of the unknown channel errors.
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