An Eight-Phase 40GHz RTWO in 28nm CMOS with Phase Noise Reduction Via Head and Tail Filtering

Unlike its low frequency counterpart, the RTWO does not benefit from the multimode nature of the resonator at high frequencies. In this paper, the limits of the traditional RTWO topology are explained and ways to approach them validated. The 40GHz demonstrator operates at twice the state of the art frequency so far realised for a RTWO in a bulk 28nm CMOS technology. In addition, an enhancement of a filtering technique that has been applied in LC oscillators is used to improve the phase noise performance in both the $1/f^{2}$ and $1/f^{3}$ regions.