Multi-carrier Adaptive Detection in Polarimetric Passive Radars

A polarimetric adaptive detection scheme based on a multichannel autoregressive process was recently proposed to improve the target detection capability of passive radar systems. Based on its demonstrated benefits, in this paper, the derived polarimetric detector is extended to the case of a passive radar simultaneously collecting signals transmitted by the same broadcast illuminator of opportunity on multiple carrier frequencies. Specifically, we derive a multi-frequency polarimetric adaptive detector that fruitfully leverages the information diversity conveyed in both the polarimetric and frequency domain. We demonstrate the effectiveness of the proposed strategy by means of an experimental validation against real data. To this aim, we make use of signals collected using an FM radio multichannel passive radar prototype, equipped with two dual-polarized antennas and able to collect signals at four frequency channels simultaneously. The application of the derived strategy also in comparison with state-of-the-art approaches shows the capability of the proposed technique to effectively increase the detection capability thanks to both a more effective rejection of the interference contribution at the single frequency channel as well as to an increased robustness with respect to time-varying characteristics of the employed waveform.