An 85-GHz Power Amplifier Utilizing a Transformer-Based Power Combiner Operating Beyond the Self-Resonance Frequency

Abstract

In this study, we demonstrate an 85-GHz eight-way four-stage power amplifier (PA) with transformer-based power combiners (PCs) and power splitters (PSs) operating beyond their self-resonance frequencies in 65-nm CMOS. An equivalent two-port network of a multiport PC/PS was developed to investigate the circuit behavior for estimating the possible operating frequency ranges and performing optimal impedance matching of the PA with PCs/PSs. From the results, the PA achieved a power gain of 29.3 dB with a 3-dB gain bandwidth recorded from 82.7 to 86.7 GHz, a saturated output power of 19.1 dBm with an output 1-dB gain compression point of 16.2 dBm, and a peak power-added efficiency of 8.6%. The total chip size is 0.72 mm(2), and the core size excluding pads is only 0.172 mm(2).