Movable Antennas for Terahertz Broadcast Beamforming in Hybrid-Field Scenarios

Given the increased likelihood of near-field effects in Terahertz (THz) communications, there is an urgent need to enhance beamforming performance in such environments. Therefore, this contribution introduces a system designed for THz broadcast beamforming that effectively operates across near-field and far-field scenarios, namely hybrid-field regions, utilizing movable antennas (MAs). Specifically, we develop a joint optimization strategy for the beamforming vector and the locations of the MAs to maximize the minimal beamforming gain. For the challenging non-convex constraints, we employ alternating optimization (AO), successive convex approximation (SCA), and semidefinite relaxation (SDR) techniques to provide necessary relaxations and feasible solutions. Finally, simulation results demonstrate that the proposed method provides about 66.7% improvement for THz broadcast beamforming in hybrid-field scenarios.