Supervised DPCA Scheme Based on Reciprocal Filter for Clutter Cancelation From Moving OFDM Radar

This article addresses the problem of target detection against clutter and noise in active/passive mobile multichannel radar systems exploiting orthogonal frequency-division multiplexing (OFDM) waveforms. It has been shown that a range compression stage based on the reciprocal filter (RF) can be used in the signal processing scheme to mitigate the effects of the time-varying waveform on the space–time clutter cancelation. However, such an approach is effective only when the received signal is fragmented into batches consisting of individual OFDM symbols. In turn, this is a strong constraint for coherent processing technique since it affects the implementation of displaced phase center antenna (DPCA) cancelation, the equivalent pulse repetition frequency with the corresponding ambiguities and SNR losses. In order to relax this constraint, supervised thresholded reciprocal filtering strategies can be used, which enable operation over batches of any length, i.e., using a non-OFDM fragmentation, thus providing greater flexibility. However, such techniques were verified to have a nonnegligible impact on the clutter cancelation capability. To overcome these limitations, we propose a complete processing scheme that integrates the multichannel clutter suppression stage into the RF supervision strategy adopted at the range compression stage. The proposed approach is referred to as the thresholded DPCA based on RF (T-DPCA-RF) and is compared to alternatives when operating against simulated scenarios for the case of a radar equipped with two receiving channels. The performed analysis shows that the T-DPCA-RF allows a better tradeoff between clutter cancelation and target SNR while reducing the complexity of the system and enhancing its flexibility in practical cases. Preliminary tests against experimental data confirm these results.