Beam-Focusing for Near-Field ISAC Systems

This paper considers near-field integrated sensing and communication (ISAC) systems, where both potential targets and communication users are located within the near-field region of a base station equipped with an extremely large-scale antenna array. Under such a scenario, we study the near-field beam-focusing design to maximize the minimum beam pattern gain for radar sensing while ensuring the communication requirements are met. We solve the corresponding non-convex optimization problem globally optimally by leveraging the semi-definite relaxation method, and also provide a low-complexity suboptimal solution. Numerical results illustrate that beam-focusing is capable of detecting multiple targets located at identical angles. By unveiling this potential, our work pioneers the application of beam-focusing to facilitate concurrent radar sensing and communication tasks.