A +2.3dBm 124–158GHz Class-C frequency quadrupler with folded-transformer based multi-phase driving

This paper presents a D-band frequency quadrupler from 124GHz to 158GHz. The design leverages a folded-transformer based passive network to generate high-quality and broadband differential quadrature driving signals with low loss for the input tone centered at 35GHz. Then, the four-phase signals drive the 1st-stage frequency doublers to yield fully differential signals at the 2nd harmonic frequency (70GHz), which feed another push-push frequency doubler and generate the desired 4th harmonic output at 140GHz. The push-push doublers are designed based on 2nd harmonic load-pull with Class-C operation for optimized output power and efficiency. The quadrupler is implemented in a 32nm CMOS SOI process occupying only 530μm-by-550μm. It achieves the state-of-the-art output power of +2.3dBm, a peak DC-to-RF efficiency of 5.3%, and the best reported -3dB bandwidth of 24% at D-band under 1.1V supply.