Secure Transmission Optimization for RIS-Aided DFRC Systems with Artificial Noise

Ensuring physical layer security is crucial for Dual-Function Radar-Communication (DFRC) systems. The synergism of Artificial Noise (AN) and Reconfigurable Intelligent Surface (RIS) is proposed to improve transmission security. Aiming to maximize the secrecy rate, beamforming for transmit signals and AN or jamming signals at the dual-function radar and base station (radar-BS), along with passive reflection phase-shift matrix (PSM) of the RIS are jointly optimized. This optimization is subject to satisfying the transmit power budget at the radar-BS, the unit modulus constraint at the RIS, and the SINR thresholds for both communication and radar sensing at the radar-BS. To render this nonconvex problem tractable, we decompose it into three convex sub-problems, which are solved by reformulating into fractional programming(FP) problems and employing the techniques of successive convex approximation (SCA) and semidefinite relaxation (SDR). Numerical simulations demonstrate that the proposed algorithm can help improve the transmission security of DFRC systems while ensuring target sensing performance.