High-Degree-of-Freedom Range--Doppler Modulation via Optimized Pseudorandom Coding Metasurface

Time-coding metasurfaces (TCM) have emerged as a promising approach for radar target feature modulation (RTFM), attracting significant attention in recent years. However, existing methods often encounter a trade-off between system complexity and modulation flexibility, with limited multidimensional control. Based on the linear discrete harmonic generation characteristics of periodic modulation TCMs, this paper establishes a grid distribution model of false targets in the range-Doppler (RD) domain. A phase-modulated reflector (PMR) system is further proposed to achieve high-degree-of-freedom joint modulation of target range and Doppler features, while maintaining system complexity comparable to that of 1-bit TCMs. The core of the system lies in periodic pseudo-random coding, which supports flexible RD feature modulation. By integrating a genetic algorithm with a suitable fitness function, the system enables customized harmonic generation, thereby redistributing real target energy over the RD grid to synthesize false target peaks at specified locations. Leveraging the multi-reflection and retro-reflection properties of corner reflectors, the system can be configured in either 1-bit or 2-bit phase modulation mode to generate symmetrically or asymmetrically distributed false targets in the RD domain, while preserving low system complexity. The proposed RTFM method is validated through both simulation and practical radar experiments, demonstrating its potential for diverse application scenarios.