Beam Squint Compensation Technology in Ultra-large-scale 3D MIMO Terahertz Systems

Terahertz communication technology has been considered as one of the promising technologies for the future 6G wireless communications with the advantage of its ultra-large bandwidth. Ultra-large-scale antenna technology can provide huge spatial diversity and improve spectrum efficiency， which also plays a key role in 6G wireless communications. In the phase-shifter based massive MIMO （multiple-input multiple-output） hybrid precoding system， due to the ultra-large bandwidth of the terahertz frequency band， the subcarrier channels with different frequencies have different equivalent spatial directions. Therefore， the beamforming at the transmitter will cause serious beam squint problems. At the same time， with the continuous increasing of antennas scale， the application of ultra-large-scale antenna technology further aggravating the loss caused by beam squint. In view of the amplification of beam squint caused by ultra-large antenna arrays， this paper uses 3D MIMO planar antenna arrays to improve this situation. In order to improve the system performance， based on the 3D massive MIMO system， this paper proposed a hybrid precoding scheme based on a two-layer phase-shifter structure， and uses the second-layer phase-shifters to compensate the subcarriers with different frequencies. Simulation results reveal that the method can effectively compensate for the array gain loss caused by beam squint and achieve near-optimal system performance.