ISAR Jamming Suppression Against Time-Modulated Metasurfaces via Optimized Dual-PRI Design and Differential Processing

Time-modulated metasurfaces (TMMs) attached to target surfaces can generate range-extended deceptive false targets by periodically modulating incident radar signals in the fast-time domain. As an open-loop jamming technique, TMM-based deceptive jamming operates without knowledge of the radar pulse repetition interval (PRI). This lack of real-time PRI awareness enables the radar to intentionally control the azimuthal displacement of the false targets by selecting a PRI that is not an integer multiple of the TMM modulation period. Exploiting this inherent vulnerability, this article proposes a jamming suppression method for inverse synthetic aperture radar (ISAR) systems based on optimized dual-PRI design and differential processing. The method first estimates the TMM modulation parameters from an initial ISAR image acquired under a baseline PRI. An optimized PRI is then designed to maximize the azimuthal separation of false target clusters between adjacent coherent processing intervals (CPIs). By alternating the PRI between the baseline and optimized values across CPIs, the radar acquires a sequence of ISAR images in which false targets shift position while the true target remains stationary. A multi-differential processing method is subsequently applied to this image sequence to suppress the false targets effectively. The feasibility and effectiveness of the proposed method are validated through extensive simulations using a 330-point aircraft model and controlled measurements in a microwave anechoic chamber. The experimental results confirm that the method achieves robust suppression of TMM-based deceptive jamming under both simulated and real-world conditions, effectively eliminating false targets while preserving the true target structure. Notably, successful suppression is demonstrated in both unambiguous and aliased ISAR imaging scenarios, validating the potential practical applicability of the approach.