Low-phase-noise 54GHz quadrature VCO and 76GHz/90GHz VCOs in 65nm CMOS process

This paper presents new circuit topologies and design techniques for low-phase-noise CMOS mmWave Quadrature VCO (QVCO) and VCOs. A transformer coupling with extra phase shift is proposed in QVCO to decouple the tradeoff between phase noise (PN) and phase error and improve the PN performance. This technique is demonstrated in a mmWave QVCO with a measured PN of −119.2dBc/Hz at 10MHz offset of a 56.2GHz carrier and a tuning range of 9.1% (FOM
T
of −179dBc/Hz). To our best knowledge, this QVCO has the lowest PN at 10MHz offset among all the QVCOs around 50–60GHz frequency range. In addition, an inductive divider feedback technique is proposed in VCO design to improve the transconductance linearity, resulting in larger signal swing and lower PN compared to the conventional LC VCOs. The effectiveness of this approach is demonstrated in a 76GHz VCO and a 90GHz VCO, both fabricated in a 65nm CMOS process, with an FOM
T
of 173.6dBc/Hz and 173.1dBc/Hz, respectively.