A 0.18-μm CMOS 16-GHz varactorless LC-VCO with 1.2-GHz tuning range

The paper describes a 16-GHz monolithic varactorless LC-tank VCO implemented in a 0.18-mum CMOS technology. Unlike the traditional tuning method by a varactor, in this work a tunable inductor, which is introduced by a transformer based on tuning currents from the active components controlled by the input voltage, is employed in the VCO. Without a varactor in the LC tank, the oscillator can easily arrive at the requirement for high-frequency operation. The VCO using a symmetry transformer provides the tuning range of 15.44 to 16.64 GHz (7.5%) at 1.8 V supply. With operating at 16-GHz frequency, the measured phase noise is -118.6 dBc/Hz at 1-MHz offset, and the VCO dissipates around 3.3 mA.