Large-scale power-combining and linearization in watt-class mmWave CMOS power amplifiers

Switching-class PAs employing device-stacking have been recently explored to meet the challenge of efficient power amplification at mmWave frequencies at moderate power levels of around 20dBm. In this paper, we propose the use of a single-step, large-scale (8-way), 75%-efficient lumped quarterwave power combiner that is co-designed with stacked Class-Elike PA unit cells to enable a Q-band 45nm SOI CMOS PA with a peak P_sat of 27.2dBm (>0.5W), peak PAE of 10.7% and 1dB flatness in P_sat over nearly the entire Q-band (3346GHz). This measured output power level is approximately 5 × higher than prior reported mmWave silicon PAs. In order to support complex modulations with high average-efficiency, we also propose a novel linearizing architecture that combines largescale power combining, supply-switching for efficiency under backoff and dynamic load modulation for linearization. A second fully-integrated 42.5GHz 45nm SOI CMOS PA is implemented based on this architecture and achieves 60% of the peak efficiency at 6dB back-off.