Design of ISAC directional modulation exploring reconfigurable intelligent surface

Directional modulation (DM) is an evolving physical layer security technology that has attracted considerable attention in recent years across both academia and industry. In this paper, a design approach for integrated sensing and communication (ISAC) systems utilizing reconfigurable intelligent surfaces (RIS) is presented. The method aims to enhance target estimation performance in the radar direction by maximizing the signal to
noise ratio (SNR) at the sensed target while preserving the intended constellation diagrams in the communication direction. Moreover, it introduces a mismatch threshold for random signals in unintended directions to disrupt the constellation patterns. The RIS serves as a relay to improve the overall performance for both the communication and radar systems by optimizing the discrete phase values.