An ultra-wideband CMOS VCO with 3-5 GHz tuning range

An ultra-wideband CMOS voltage-controlled oscillator (VCO) with 3-5 GHz tuning range is presented in this paper. The circuit was designed and fabricated by using TSMC 0.18-/spl mu/m CMOS process. The proposed VCO is using the tunable active inductor to replace the passive spiral inductor. The active inductor can vary the inductance between 1.5/spl sim/7 nH with quality-factor > 30 by a feedback tunable resistor. Comparisons of this topology with conventional VCO show that this topology achieves better performance with very wide tuning range and compact chip size. The tuning range is approximately from 3 to 5 GHz for ultra-wideband system applications.