Interrupted Sampling Repeater Jamming Suppression with Pulse Doppler Radar Using Linear Interpulse Frequency Coding

Interrupted sampling repeater jamming (ISRJ) is an advanced form of coherent jamming, and the suppression of this jamming has become a critical problem for modern radar electronic countermeasures. In this paper, we propose a countermeasure based on the linear interpulse frequency- coding linear frequency modulation (LIFC-LFM) signal. The LIFC refers to the linear encoding of the frequency of each pulse transmitted by the radar system, which can change the distribution of the false targets formed by ISRJ in the range-Doppler (RD) spectrum. In this context, we design the frequency coding value to effectively separate the true and false targets in the RD spectrum. Furthermore, we propose a fast-time phase compensation method to separate the true and false targets in the Doppler dimension to facilitate false target suppression. Finally, ISRJ can be suppressed by oblique projection processing. Simulation examples demonstrate that the proposed method has an excellent and robust ISRJ suppression effect for direct forwarding ISRJ, repeated forwarding ISRJ, and frequency shifting ISRJ. Meanwhile, the signal-to-noise ratio loss caused by the jamming suppression is small.