A wide tuning range CMOS VCO using variable inductor

The paper presents a novel wide tuning range CMOS VCO using an on-chip variable inductor as an additional variable element to extend tuning range. The VCO was fabricated using standard 0.35 /spl mu/m CMOS process with three metal layers, and could be tuned widely from 2.13 GHz to 3.28 GHz without degradation of phase noise.