The design of a 1 V, 1 GHz CMOS VCO circuit with in-phase and quadrature-phase outputs

A CMOS ring-oscillator type VCO circuit with inphase (I) and quadrature-phase (Q) outputs has been designed by using 0.6 /spl mu/m MOS devices. This VCO has demonstrated 1 V and 1 GHz operational capabilities. Two differential delay cells has been used as one delay section and the transitions of the delay cell outputs have been combined, and thus the 1 GHz 1/Q output generation has been realized. The current-mode approach throughout the design has resulted in the extremely low voltage operation. The simulation results show more than 1.4 GHz oscillation frequency from a 1 V power supply, and less than /spl plusmn/1 phase error for I/Q outputs when Vth variation is 10 mV.