A Fast and Doppler Robust Clutter Suppression Algorithm for OFDM Passive Radar

In passive radar processing, noncooperative orthogonal frequency division multiplexing (OFDM) signals are not designed for radar purposes, and the direct path together with multipath clutter produces a high ambiguity floor that makes weak targets difficult to detect. To improve the signal-To-clutter ratio (SCR), subcarrier-domain suppression methods represented by the extensive cancellation algorithm by subcarrier (ECA-C) family are commonly employed. However, when the clutter exhibits Doppler shifts, the orthogonality among subcarriers is disrupted, leading to a degradation in suppression performance. To address this issue, this article proposes fast extensive cancellation algorithm by subcarrier and Doppler shift (FECA-CD). FECA-CD shifts clutter Doppler components toward 0 Hz, effectively reducing the degree of template mismatch arising from intercarrier interference. At the same time, the projection operator can be reused, which substantially reduces computational cost. Performance analysis reveals that FECA-CD is nearly insensitive to clutter Doppler frequency. Simulation results demonstrate that FECA-CD forms a wide and deep suppression notch across the entire clutter region and achieves substantially improved SCR compared with traditional ECA-C methods. Real-world experiments further validate that FECA-CD can reliably reveal targets hidden beneath high-Doppler multipath clutter, demonstrating its potential to broaden the practical operating scenarios of OFDM-based passive radar.