Cosinusoidal Phase Modulation Jamming Using Tunable Metasurface Against SAR–GMTI

Ground moving target indication (GMTI) in the synthetic aperture radar (SAR) system enables high-resolution, all-weather, and all-day imaging and detection of moving targets, posing a significant threat to high-value moving targets. Inspired by the flexible modulation capability of the electromagnetic metasurface technique, a cosinusoidal phase modulation jamming method based on tunable metasurfaces against the SAR-GMTI system is proposed in this paper. Firstly, the cosinusoidal phase modulation signal model generated by the tunable metasurface is investigated and discussed. Benefiting from the continuous phase control as well as flexibly adjustable modulation index and modulation frequency of the cosinusoidal phase modulation, the jamming signal with multiple false moving targets can be effectively constructed with a small phase variation. This characteristic effectively broadens the operational bandwidth. Subsequently, a novel dual-polarized tunable metasurface based on varactors is designed and implemented to achieve continuous phase modulation of radar signals. Owing to the rotational symmetry of the back-to-back open-ring resonators, the proposed metasurface enables independent and flexible control of two orthogonal polarizations. On this basis, the SAR-GMTI jamming performance of the cosinusoidal phase modulation with different modulation indices and modulation frequencies generated by the designed tunable metasurface is comprehensively analyzed theoretically and experimentally verified. It indicates that the high-quality SAR-GMTI jamming performance with high fidelity and flexibility can be achieved by appropriately adjusting the values of the modulation index and the modulation frequency, generating and detecting multiple false moving targets with different azimuth positions and large amplitudes at low SCNR while ensuring a small phase range.