A 2.5-3.2ghz Cmos Differentially-Controlled Continuously-Tuned Varactor-Less Lc-Vco

The design and implementation of a 2.5-3.2GHz LC-VCO incorporating a varactor-less tuning technique is presented. The VCO's oscillation frequency is tuned differentially by varying the effective inductance of the oscillators. Fabricated in a 0.18 mu m CMOS process, the prototype VCO achieves 24% continuous tuning range without varactors. The circuit draws 7-15mA current from a 1.8V power supply. The measured phase noise is varying between -102dBc/Hz and -111 dBc/Hz at 1MHz offset across the tuning range.