A 100GHz active-varactor VCO and a bi-directionally injection-locked loop in 65nm CMOS

A 100GHz fundamental active-varactor VCO and a bi-directionally injection-locked loop are demonstrated in 65nm CMOS. Without using a conventional passive varactor, the proposed VCO achieves a tuning range of 5.2% at 100GHz and a phase noise of -112.1dBc/Hz at 10MHz offset. By utilizing the proposed transmission-line-based capacitive coupling, four oscillators are injection-locked properly and the loop creates eight phases of the carrier and 6dB(=10log4) of phase noise improvement, realizing a measured phase noise is -118.8dBc/Hz at 10MHz offset.