Wide tuning range LC-oscillator in 65nm SOI CMOS, based on switchable secondary inductor

An LC-based VCO in standard 65nm CMOS SOI technology is presented. The VCO exhibits a measured tuning range 6.4-11.3GHz. The tuning range is significantly extended by a combination of switchable inductor and capacitor banks. The switchable inductor consists of two magnetically coupled spiral inductors. The secondary coil can be either open or closed with a large FET switch, which in closed condition significantly reduces the inductance of the main coil by means of mutual inductance.