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 0.18μm 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 −111dBc/Hz at 1MHz offset across the tuning range.