Hybrid Precoding With Time-Modulated Arrays for Mmwave MIMO Systems

We consider the utilization of time-modulated arrays (TMAs) as a simple and cost-effective approach to hybrid digital–analog precoding in millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems. Instead of conventional variable phase shifters (VPSs), our proposed TMA hybrid precoders use radio frequency (RF) switches followed by 1-bit VPSs in the analog part. We study the insertion losses at mmWave of a TMA analog precoding network in terms of sideband radiation and hardware efficiency. In addition, we present different algorithms for the design of both the baseband and RF parts of a TMA hybrid precoder. The proposed methods exhibit different tradeoffs between performance, complexity, and power efficiency. Finally, TMA precoders are compared to those implemented with conventional VPSs in terms of insertion losses, chip area, and cost, concluding that precoding with TMAs is a competitive solution for mmWave MIMO systems.