A 12.5 GHz back-gate tuned CMOS voltage controlled oscillator

This paper presents the design and measurements of a 12.5 GHz CMOS VCO. The circuit is an LC oscillator using an integrated octagonal differential inductor. The VCO is fully integrated and fabricated in a standard 0.35 /spl mu/m CMOS process. The frequency is tuned using the back-gate voltages of a PMOS cross-coupled differential pair. The tuning range of the VCO is 300 MHz. The maximum achieved frequency of operation is 12.5 GHz using a 3.5 V power supply. The measured phase noise at 100 MHz offset is -85 dBc/Hz. The design is optimized for high frequency operation, achieving the highest oscillation frequency for a CMOS VCO of this type to be published to date.