RIS-Aided Wideband DFRC with Reconfigurable Holographic Surface

Dual-function radar-communications (DFRC) systems generally employ reconfigurable intelligent surface (RIS) as a reflector in the wireless media to enable non-line-of-sight (NLoS) sensing and communications. Different from RIS, reconfigurable holographic surface (RHS) are the surfaces with an embedded feed. These surfaces are deployed at the transceiver thereby leading to a lightweight design and greater control of the radiation amplitude. In this paper, we propose a novel frequency-selective RIS-assisted wideband DFRC system that is also equipped with a RHS at the transceiver. Our goal is to jointly design the digital, holographic, and passive beam-formers to maximize the radar signal-to-interference-plus-noise ratio (SINR) while ensuring the communication SINR among all users. The resulting nonconvex optimization problem involves maximin objective and difference of convex constraint. We develop an alternating maximization framework to decouple and iteratively solve these subproblems. Numerical experiments demonstrate that the proposed method achieves better radar performance than non-RHS, non-RIS, and randomly-configured RIS-aided DFRC systems.