A 1.8GHz CMOS quadrature voltage-controlled oscillator (VCO) using the constant-current LC ring oscillator structure

A new fully integrated CMOS quadrature voltage-controlled oscillator (VCO) realized in a standard 0.5 mu m double poly double metal (DPDM) CMOS technology is proposed, that combines a fully differential two-stage ring oscillator with LC tanks and negative resistance to provide both inphase and quadrature output signals. The phase noise is low due to the use of the resonator-type oscillator. The simulation results show that with an on-chip varactor tuned resonator and a control voltage of 0-3 V, the tuning range of the VCO is 160MHz from 1.67GHz to 1.83GHz. Under 1% mismatch of the inductor or capacitor, the phase error of VCO outputs are less than 1 degrees from perfect quadrature and the amplitude ratio are less than 1.0007. The power dissipation is 35mW for 3V power supply. The area is 1.3 x 0.9 mm(2), dominated by the two integrated spiral inductors.