Low phase noise and linear gain VCO using self-switched biasing

A low power and low phase noise LC-tank VCO with linear gain for 2.4 GHz ISM band is presented. Self-switched biasing technology is adopted to reduce flicker noise. Low power consumption is achieved by reducing supply voltage for the character of this structure. To extend the linear range of VCO gain (Kvco) in low supply voltage condition, distributed varactor biasing is used. The proposed VCO is implemented in 0.18μm CMOS process. The measured phase noise is −122.9 dBc/Hz at 1MHz offset from 2.5 GHz oscillation frequency, while consuming 2.6 mA current with 1.2 V supply voltage, and the FOM is 186 dBc/Hz.