Phase noise in a differential CMOS voltage-controlled oscillator for RF applications

This paper presents theoretical and experimental results on phase noise of differential CMOS oscillators. A simple analytical expression is derived and verified by simulation which relates the phase noise including the device excess noise factor to circuit parameters. In agreement with the theoretical results, an experimental 1.9-GHz oscillator yielded phase noise as low as -100 dBc/Hz at 100-kHz offset at a power consumption of 12 mW. A wide tuning range of 250 MHz was obtained by using PMOSFET's as varicap with only slight degradation of the phase-noise performance due to the varicap.