A High Swing Low Power CMOS Differential Voltage-Controlled Ring Oscillator

This paper presents the design of a two-stage CMOS differential voltage-controlled ring oscillator (VCO). The VCO is designed to operate as a module of the frequency synthesizer in a PLL to generate the local oscillator (LO) of a multi-band acquisition system, providing quadrature output. The goal is a wide operating frequency tuning range of 440 MHz-1.4 GHz in the VCO with low power consumption, 90 dBc/Hz @ 600 KHz phase-noise performance and good linearity between the frequency and control voltage. Simulation results verify the theoretical development as well as the final layout design. The symmetric load transistor operation region controls the frequency behavior achieved by the ring VCO, which shows a monotonic relation with the control voltage when the loads are operated in saturation. The circuit was designed, implemented and simulated in a 0.18 mum IBM CMOS technology.