SAR Anti-Interrupted-Sampling-Repeater-Jamming Method Based on Subpulse Permutation Linear Frequency Modulation

Abstract

To address the difficulties in detecting and extracting parameters of interrupted sampling repeater jamming (ISRJ) in synthetic aperture radar (SAR) due to strong echo masking and transform domain feature aliasing in complex land and sea scenarios, this article proposes an active–passive joint countermeasure method based on a subpulse permutation linear frequency modulated (SP-LFM) waveform. At the transmitter, the LFM signal is segmented and encoded with pseudorandom timing, creating a distinctive spectral notch structure. This design actively establishes a feature discrepancy between the jamming signal and the scene echoes within the receiving processing chain. At the receiver, a frequency-domain inverse weighting (FDIW) processing method is proposed, which significantly enhances the otherwise obscured jamming signal from the echo background. Furthermore, by utilizing the deterministic time–frequency mapping inherent in the waveform, the temporal sampling parameters of the jammer are estimated from the reconstructed jamming spectral support obtained after notch-constrained peak extraction. The estimation accuracy is further improved through multipulse joint processing. Simulation results demonstrate that the proposed method effectively detects ISRJ and extracts its parameters while preserving SAR imaging quality.