A VERY LOW NOISE WIDEBAND CLASS-C CMOS LC VCO

In this paper, a new class-C voltage-controlled oscillator (VCO) is presented. In the proposed VCO, the tail capacitor of the conventional class-C oscillator is dislocated from the source of the cross-coupled transistors to their gate to achieve a rail-to-rail output swing. This improves the phase noise by 2.9 dB compared to the conventional class-C one. Besides, a new switching scheme is presented in the switched capacitor bank used for coarse tuning of the proposed VCO to lower the on resistance of the switches as well as to reduce the parasitic capacitors. This wide tuning range class-C VCO is designed in a 0.18 mu m CMOS technology. It achieves a -125.3 dBc/Hz phase noise at 1MHz offset from a 2.2 GHz carrier frequency while covering a wide tuning range from 1.82 to 2.65 GHz and consuming 3.5mW power from a single 0.9V power supply.