Low-Resolution Architectures for Power-Efficient Scaling of mmWave Phased Array Receivers

Utilizing mmWave massive MIMO frontends for base station to mobile communication promises unprecedented throughput gains in cellular networks. Power efficiency is a significant bottleneck in scaling to the large array sizes required for closing the link at high frequencies, particularly in the battery-powered handset. Conventional phased array architectures at 100+ GHz require close to 100 mW of power per receive antenna, making them ill-suited for scaling to massive arrays. In this paper, we propose drastically simplified receiver frontend designs that are predicted to slash this per-channel wattage by an order of magnitude or more at 140 GHz. These power savings come at the cost of imperfect beamforming and under-utilization of the array elements and die area. We quantify these tradeoffs for our baseline on-off architecture, as well as 1-bit and 2-bit phase switched arrays. In the lowest resolution setting, on-off beamforming, we show that beamforming efficiency of 70% is achieved with 40% utilization of the aperture. This tradeoff improves significantly with the adoption of even the most coarse (1 or 2 bit) phase control, motivating us to pursue power-optimized designs for low-precision mmWave phase shifters.