Phase noise optimization of a self-cascode VCO by changing the capacitor ratio and substrate bias

This paper reports a low-voltage low-power self-cascode VCO with a phase noise optimization technique. Self-cascode structure with capacitive feedback network provides better phase noise performance without degrading the voltage headroom. Phase noise performance of the proposed VCO has been optimized by an optimum selection of capacitor ratio. Fabricated in a 0.18-μm RF CMOS process, the oscillator can work with a supply voltage of 1.0 V, with an operating frequency of 1.30 GHz while providing a phase noise of -114.48 dBc/Hz at 1 MHz offset and an output power of -22.27 dBm. Measurement results indicate that an optimum substrate bias ensures the minimization of phase noise.