Robust ISAC Beamformer Utilizing Angular Distributions of Target and Clutters

In this paper, we aim to design an ISAC beamforming technique that is robust to angle estimation errors of both target and clutters, in multi-user and single-target MIMO ISAC systems. To this end, the proposed ISAC beamformer is designed to maximize the average signal-to-clutter-plus-noise ratio (SCNR) with respect to the angular distributions of the target and clutters, while ensuring signal-to-interference-plus-noise ratio (SINR) threshold for each communication user. Since calculating the average SCNR is highly complex, we derive a lower bound for the average SCNR and approximated it with simple closed form expression. Additionally, we use Dinkelbach’s transform and SDR (semidefinite relaxation) to resolve the non-convexity of the optimization problem. Numerical simulations demonstrate that the proposed beamformer achieves higher sensing performance in average sense, compared to the estimated angle-based beamformer, which indicates that the proposed beamforming framework is robust to angle estimation errors for both target and clutters.