Max-Min Beamformer for THz Wideband Communications

Analog beamforming is appealing for future terahertz (THz) communications since it can generate high-gain directional beams with low-cost phase shifters. However, the conventional analog beamforming based on array response vector to steer a narrow beam may suffer from severe performance loss in wideband systems due to the "beam squint" effect over frequency. To tackle this issue, we propose a new max-min beamformer design in this paper for THz wideband communication systems, which aims to maximize the minimum beam gain over the entire frequency band. To solve this challenging problem, an augmented Lagrange method (ALM) is proposed to obtain a high-quality solution with low complexity. Numerical results show that the proposed beam design can yield considerably better performance than the conventional narrowband beamformer, especially in the case of large angle of departure (AoD) from the base station (BS) to the user.