Dynamic-subarray with Fixed-true-time-delay Architecture for Terahertz Wideband Hybrid Beamforming

Hybrid beamforming for Terahertz (THz) ultra-massive MIMO (UM-MIMO) systems is a promising technology for 6G networks, which can overcome huge propagation loss and offer unprecedented data rates. With ultra-wide band-width in THz band, the beam squint becomes one of critical problems which could reduce the array gain and degrade the data rate. However, the traditional phase-shifters-based hybrid beamforming architectures cannot tackle this issue due to the frequency-flat property of the phase shifters. In this paper, to combat this beam squint yet with reduced power consumption, a novel dynamic-subarray with fixed-true-time-delay (DS-FTTD) architecture is proposed. Furthermore, a low-complexity row-decomposition (RD) algorithm is developed for the DS-FTTD architecture. Extensive simulation results show that, by using the RD algorithm, the DS-FTTD architecture achieves signifi-cantly higher array gain and spectral efficiency than the phase-shifters-based architectures. Meanwhile, the energy efficiency is substantially improved thanks to the low-cost FTTDs.