A low-phase noise 5-GHz CCNF Colpitts VCO with parallel-branch inductors

In this paper, we propose both the 5 GHz CCNF Colpitts LC-tank VCO with less flicker noise upconversion and the parallel-branch inductor with 12 % Q-factor improvement. The proposed CCNF Colpitts LC-tank VCO suppresses flicker noise induced low-frequency noise of the conventional Colpitts differential pair as well as the high-frequency thermal noise of tail current. Therefore, the proposed CCNF LC-tank VCO represents about 25-dB improvement of phase noise compared to the conventional Colpitts LC-tank VCO. In this paper, two kinds of VCOs have been manufactured using SiGe HBT process technology, and consume 12 mA at 2 V bias voltage.