Wideband Beamforming for Hybrid Massive MIMO Terahertz Communications

The combination of large bandwidth at terahertz (THz) and the number antennas in massive MIMO results non-negligible spatial wideband effect time domain or corresponding beam squint issue frequency domain, which will cause severe performance degradation if not properly treated. In particular, for a phased array based hybrid transceiver, there exists contradiction between requirement mitigating hardware implementation analog beamformer/combiner, makes accurate beamforming an enormous challenge. this paper, we propose two approaches, on virtual sub-array true-time-delay (TTD) lines, respectively, to eliminate impact squint. former one divides whole into several sub-arrays generate wider provides evenly distributed gain across operating band. To further enhance thoroughly address aforementioned contradiction, latter introduces TTD lines new beamformer/combiner. This TTD-aided enables achieves near-optimal close full-digital transceivers. Analytical numerical demonstrate effectiveness proposed approaches.