2012 Volume 9 Issue 24 Pages 1881-1886
This paper proposes a low-power, low close-in phase-noise voltage-controlled oscillator (VCO) based on Colpitts oscillator. The VCO stacks the Colpitts VCO with a negative conductance cell. By exploiting a bias-level shifting technique, the proposed VCO provides larger output swing, and the close-in phase noise characteristics is improved impressively while consuming very low power. The proposed VCO is designed and simulated in 65nm CMOS technology operating at 2.6GHz with only 0.12mA core current consumption from 0.5V supply voltage. The simulated phase noise of the proposed VCO is -27.6dBc/Hz at 100Hz offset, -54.4dBc/Hz at 1kHz offset, and -117.7dBc/Hz at 1MHz offset frequency, respectively. The calculated figure of merit (FOM) is about -198dBc/Hz at 1MHz offset. Compared to that of the conventional VCO, the phase noise performance is significantly improved by more than 20dB from 100Hz to 1kHz offset, around 15dB at 10kHz offset, and 6dB at 1MHz offset frequency, respectively.
