Radio frequency interference mitigation in OFDM based passive bistatic radar

Abstract

High frequency passive bistatic radar (HFPBR) is a novel and promising technique in development. DRM broadcast exploiting orthogonal frequency division multiplexing (OFDM) is accepted as the only standard for HF band by ITU-R. DRM broadcast transmitters supply good choice for the illuminator of HFPBR. HFPBR based on DRM broadcast is a beneficial supplement to the active HF radar. HFPBR working in crowded short wave band, as the active radar, faces with radio frequency interference (RFI) problem. The traditional amplitude modulation (AM) broadcasts are ones of the main RFI resources. Unlike the active radar, RFI will affect the reference signal reconstruction quality in HFPBR with OFDM waveform, which will directly affect the performance of direct-path wave and multipath clutter rejection. Direct-path wave and multipath clutter rejection are a stumbling block for target detection of HFPBR. As the direct-path wave and multipath clutter do, RFI also will mask potential target echoes. RFI mitigation has to share the system's degree of freedom with clutter rejection. In order not to occupy the system's degree of freedom, a temporal RFI mitigation algorithm is proposed to cope with the AM interferences, after RFI model and impacts analysis on HFPBR with new radar waveform. The proposed algorithm is a closed-form approximate maximum likelihood estimator, which is easy to perform. The impacts analysis of RFI and the RFI mitigation algorithm performance are evaluated using the simulation and experimental data of DRM-based HFPBR.