A 3.01–3.82 GHz CMOS LC voltage-controlled oscillator with 6.29% VCO-gain variation for WLAN applications

A wideband low-phase-noise LC voltage-controlled oscillator(VCO) with low VCO gain(KVCO/ variation for WLAN fractional-N frequency synthesizer application is proposed and designed on a 0.13-m CMOS process. In order to achieve a low KVCO variation, an extra switched varactor array was added to the LC tank with the conventional switched capacitor array. Based on the proposed switched varactor array compensation technique,the measured KVCO is 43 MHz/V with only 6.29% variation across the entire tuning range. The proposed VCO provides a tuning range of 23.7% from 3.01 to 3.82 GHz, while consuming 9 mA of quiescent current from a 2.3 V supply. The VCO shows a low phase noise of –121.94 dBc/Hz at 1 MHz offset, from the 3.6 GHz carrier.