Coupled Inverter Ring I/Q Oscillator for Low Power Frequency Synthesis

Abstract

A novel 12-stage VCO with in-phase and quadrature outputs at the 3rd harmonic of the oscillating frequency is presented. It employs coupled inverter rings. A new linear model of coupled inverter rings is developed to identify all possible oscillating modes and their frequencies using the Barkhausen criterion. A frequency synthesizer implemented in 0.18mum CMOS with such a VCO has wide tuning range, and consumes only 2.8mA from a 1.5V supply to generate 2.4GHz differential I/Q outputs