Low-phase-noise 3.4–4.5 GHz dynamic-bias class-C CMOS VCOs with a FoM of 191 dBc/Hz

This paper presents two class-C CMOS VCOs with a dynamic bias of the core transistors, which maximizes the oscillation amplitude without compromising the robustness of the oscillation start-up. The VCOs have been implemented in a 90 nm CMOS process and cover the frequency band between 3.4 GHz and 4.5 GHz, for a 28% tuning range. Drawing 5.5 mA from 1.2 V, the phase noise is lower than -152 dBc/Hz at a 20 MHz offset from a 4 GHz carrier. The resulting phase-noise FoM is 191 dBc/Hz and varies less than 1 dB across the tuning range.