A pulse-tail-feedback VCO achieving FoM of 195dBc/Hz with flicker noise corner of 700Hz

This paper proposes a pulse-tail-feedback technique for improving both 1/f
²
and 1/f
³
noises. The proposed VCO has separated tail transistors driven by inverters with rail-to-rail voltage swing. The tail transistor has an impulse shaped current waveform to improve FoM, and the flicker noise up-conversion is reduced by the switching operation. A prototype of the proposed VCO is implemented in 180nm CMOS, and the VCO achieves an FoM of 195dBc/Hz from 10kHz-10MHz offset with a flicker noise corner of 700Hz at 4.55GHz oscillation.