A 1.8 GHz 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 μm 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 in-phase 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 160 MHz from 1.67 GHz to 1.83 GHz. Under 1% mismatch of the inductor or capacitor, the phase errors of VCO outputs are less than 1° from perfect quadrature and the amplitude ratio are less than 1.0007. The power dissipation is 35 mW for 3 V power supply. The area is 1.3×0.9 mm², dominated by the two integrated spiral inductors