Receive Beamforming Using Sum and Difference Virtual Coarrays for Dual-Function Radar Communications

The dual-function radar and communication (DFRC) system addresses the problem of radio frequency congestion. Sparse arrays can reduce system cost and increase array aperture by constructing virtual co-arrays. In this paper, we consider the problem of receiving beamforming with sum and difference co arrays in the DFRC system. Firstly, we present the radar and communication signal models with difference and sum co-arrays in the DFRC system. Then, different receive beamforming methods are proposed to handle situations where radar targets and commu nication users are located at the same or different angles. When radar targets and communication users are at different angles, an optimal beamforming scheme is designed to assign them to separate beams. When a radar target and a communication user are at the same angle, we consider an orthogonality constraint to mitigate the radar and communication cross-interference in the same beam. We compared the beamforming performance of different sparse array structures, including coprime, nested array, nestedR array, and their virtual arrays, i.e., difference co-array or sum co-array. Simulation results demonstrate that the sparse array beamforming scheme enhances the resolution of receive beamforming in the DFRC system and reduces the cross-interference between received communication and radar signals.