Null Space Projection-Based Design of Multibeam for Joint Communication and Sensing Systems

This article proposes a multibeam combining method for joint communication and sensing (JCAS) systems. A sensing beamforming (BF) vector is designed to have components only in the orthogonal subspace of the communication BF vector by using a null space projection. In addition, a sensing beam-centric coherence combining is adopted to align the phases of the communication beam and the sensing beam at the sensing beam direction. The proposed approach allows the communication channel to remain stable while scanning the region of interest with the combined beams. The sensing BF gain is also improved by making the sidelobe of the communication beam contribute to increasing the BF gain of the sensing beam. Simulation results are provided to verify the effectiveness of the proposed method.