High-Efficiency Class-E Power Amplifiers for mmWave Radar Sensors: Design and Implementation

This article presents high-efficiency power amplifiers (PAs) implemented in Texas Instruments' (TI) 130-nm BiCMOS process for V - and E -band millimeter-wave (mmWave) radar sensors. A new Class-E output network based on a doubly tuned (DT) transformer is proposed to enable high-efficiency mmWave operation. The proposed Class-E network allows increasing PA device size beyond the traditional Class-E design limits while preserving nonoverlapping Class-E current and voltage waveforms. Design examples for single-ended and differential implementation of the proposed Class-E network are presented in this article. Three PA prototypes (a 79-GHz two-stage PA, a 63-GHz single-stage PA, and a 79-GHz single-stage PA) have been designed and fabricated in a high-volume production 130-nm BiCMOS process. A Class-E interstage network with a split-and-combine 45° transformer is employed in the two-stage PA to ease driving the last stage PA devices. Device layout optimization for improved efficiency is described in this article. The measurement results achieve a peak power-added efficiency (PAE) of 30.5%/34.7%/32.6% with an output power of 17/18.1/17 dBm for the 79-GHz two-stage, 63-GHz single-stage, and 79-GHz single-stage PAs, respectively. To the best of our knowledge, these are the record PAE numbers reported for V - and E -band PAs in any silicon process, demonstrating the efficacy of the proposed DT transformer-based Class-E output network.