A wide tuning-range CMOS VCO with a tunable active inductor

This study describes a wide tuning-range VCO using tunable active inductor (TAI) topology and cross-coupled pair configuration for radio frequency operation. The TAI used two feedback loops to form a cascode circuit to obtain more degrees of freedom for inductance value. The TAI-VCO was fabricated using a 0.18 μm CMOS technology. The coarse frequency tuning is achieved by TAIs while the fine tuning is controlled by varactors. The fabricated circuit provides an output frequency range from 0.6 to 7.2 GHz (169%). The measured phase noise is from -110.38 to -86.01 dBc/Hz at a 1 MHz offset and output power is from -11.11 to -3.89 dBm within the entire frequency range under a 1.8 V power supply.