A wide band CMOS differential voltage-controlled ring oscillator

This paper presents the design of a wide band two-stage CMOS voltage-controlled ring oscillator based on the Maneatis cell. The VCO is designed for a frequency synthesizer module that generates local oscillation (LO) frequencies over a large bandwidth, targeting a multi-band acquisition system. The goal is a wide operating frequency tuning range of 400 MHz - 1.4 GHz in the VCO with low power consumption, -80 dBc/Hz@600 KHz phase-noise performance and a good linearity for the frequency and control voltage characteristics. Simulation results verify the theoretical development and measurement results validate the design. The symmetric load transistor operation region controls the frequency behavior achieved by the VCO, which shows a monotonic relation with the control voltage when the loads are operated in saturation. The prototype chip was fabricated using a 0.18mum IBM CMOS technology.