Intelligent Reflecting Surface Aided Secure Dual-Functional Radar and Communication System

In this paper, we investigate an intelligent reflecting surface (IRS) aided secure dual-functional radar and communication system where a dual-functional base station (BS) desires to securely deliver messages to an intended receiver and detect a malicious radar target simultaneously with the aid of an IRS. We generate two separate beams towards the receiver and target, respectively, while using an integrated waveform. We aim to maximize the secrecy rate while satisfying the radar detection constraint by jointly designing the power allocation factor between the two beams, the beamforming vector w at the BS and the phase shift matrix Q at the IRS. We propose the Riemannian conjugate gradient (RCG) algorithm based alternating optimization (AO) scheme to solve the formulated non-convex problem for any given epsilon. To be specific, we first use the penalty function method to reformulate the original problem and then iteratively design w and Q leveraging the RCG algorithm. We finally search the optimal epsilon numerically. Simulation results demonstrate the significance of IRS in achieving a secure DFRC system and uncover the tradeoff between the performance of secure transmission and radar detection.