ISRJ Suppression for MIMO Distributed Coherent Aperture Radar Using Bidirectional Chirps and Biorthogonal Fourier Analysis

Distributed coherent aperture radar (DCAR) operating in multiple-input multiple-output (MIMO) mode is highly susceptible to interrupted sampling repeater jamming (ISRJ). Because ISRJ consists of partially sampled slices of multiple orthogonal waveforms, its effective suppression remains challenging. To exploit both the operational characteristics of MIMO DCAR and the formation mechanism of ISRJ, this paper proposes a jamming suppression algorithm that combines up-chirp (UC) and down-chirp (DC) waveform transmission with the biorthogonal Fourier transform (BFT). First, a bidirectional double sliding window pulse edge detector is employed to estimate and compensate for transmission path delay differences among channels. Next, BFT-based analysis is applied to separate UC- and DC-associated components in the received echoes, thereby suppressing cross-term energy leakage in multi-channel matched-filter outputs. Finally, leveraging the time-frequency similarity of jamming slices originating from orthogonal waveforms, the contaminated echo segments are partitioned in a piecewise manner and mitigated via frequency-phase compensation. Simulation results demonstrate that the proposed algorithm achieves effective cross-term suppression and ISRJ cancellation while preserving system coherence.