A 1.94 to 2.55 GHz, 3.6 to 4.77 GHz Tunable CMOS VCO Based on Double-Tuned, Double-Driven Coupled Resonators Burak Çatlı, Student Member , IEEE, and Mona

Abstract

This paper presents a multi-band CMOS VCO using a double-tuned, current-driven transformer load. The dual fre- quency range oscillator is based on enabling/disabling the driving current in the secondary port of the transformer. This approach eliminates the effect of switches connected directly to the VCO tank whose capacitance and on-resistance affect both the tuning range and the phase noise of a typical multi-band oscillator. The rela- tion between the coupling coefficient of the transformer load, se- lection of frequency bands, and the resulting quality factor at each band is investigated. The concept is validated through measure- ment results from a prototype fabricated in 0.25 m CMOS tech- nology. The VCO has a measured tuning range of 1.94 to 2.55 GHz for the low frequency range and 3.6 to 4.77 GHz for the high fre- quency range. It draws a current of 1 mA from 1.8 V supply with a measured phase noise of 116 dBc/Hz at 1 MHz offset from a 2.55 GHz carrier. For the high frequency band, the VCO draws 10.1 mA from the same supply with a phase noise of 122.8 dBc/Hz at 1 MHz offset from a 4.77 GHz carrier.