G(m)- and Swing-Enhanced Colpitts VCO by Optimization of Capacitance Ratio

Abstract

This letter presents a negative conductance (G(m))- and swing-enhanced Colpitts voltage-controlled oscillator (VCO) based on optimization of the capacitance ratio. In the proposed VCO structure, a current source typically used in conventional VCOs is replaced with an inductor to increase the output voltage swing. A current-reuse configuration is also adopted to decrease power consumption. Theoretical analyses and simulations show that the devised VCO with an optimized capacitance ratio exhibits enhanced G(m) and swing when compared to a conventional VCO. Measurements revealed a phase noise of -129.67 dBc/Hz at a 1-MHz offset frequency from the 2.2-GHz carrier, while power consumption was 2.2 mW from a 1.2-V supply voltage. This resulted in a figure-of-merit of -193.1 dBc/Hz. The proposed device was implemented using a 65-nm CMOS process.