Improved SAR Interrupted-Sampling Repeater Jamming Countermeasure Based on Waveform Agility and Mismatched Filter Design

The interrupted-sampling repeater jamming (ISRJ) countermeasure is researched based on waveform agility and mismatched filter design in this work. By analyzing the effects of transmitted waveform on ISRJ imaging characteristic, the principle of the anti-ISRJ method is proposed. The ISRJ range processing gain and energy can be suppressed by designing the waveform and mismatched filter. Meanwhile, the ISRJ azimuth processing gain can be further restrained by utilizing the waveform agility. The anti-ISRJ problem is formulated and is then divided into several subproblems. The analytical solutions of waveform and mismatched filter are derived based on majorization minimization (MM), and a fast algorithm is proposed by applying a squared iterative method (SQUAREM). The fast implementation of the algorithm is derived, and computational complexity is O(N log N). Moreover, to improve the anti-ISRJ performance, the peak-to-average power ratio (PAR) constraint is introduced. Specifically, the waveform design subproblem under PAR constraint is solved, and thus, the PAR waveform can also be designed by the proposed algorithm. The simulation results verify that the proposed joint design algorithm shows significantly faster running speed than the conventional algorithms. The anti-ISRJ performance is superior to the existing methods, and the best anti-ISRJ performance can be obtained by applying the PAR waveform agility and mismatched filter design method.