Non-Uniform Linear Arrays for Target Detection and DoA Estimation in Passive Radar STAP

This paper explores the use of Non-Uniform Linear Array (NULA) configurations for target detection and Direction of Arrival (DoA) estimation in mobile passive radar systems. By leveraging on spatial diversity, NULAs are shown to potentially improve the flexibility and performance of a SpaceTime Adaptive Processing (STAP) scheme, when few spatial receiving channels are available, as is typically the case of passive radar. The impact of NULAs on clutter suppression performance is analysed, showing that a narrower cancellation notch can be obtained, enhancing the detection of slow-moving targets, while still preventing the comparison of blind velocities. Moreover, resorting to a non-uniform distribution of the antennas, the trade-off between DoA estimation accuracy and unambiguous angular sector can be relaxed. A larger displacement between the phase centres is shown to reduce the DoA estimation error of unambiguous targets. The advantages of the proposed solution are demonstrated against simulated data, addressing the case of a mobile passive radar exploiting DVB-T as a signal of opportunity.