Design and analysis of a three-stage voltage-controlled ring oscillator

This paper describes a large tuning range low phase noise voltage-controlled ring oscillator(ring VCO)based on a different cascade voltage logic delay cell with current-source load to change the current of output node.The method for optimization is presented.Furthermore,the analysis of performance of the proposed ring VCO is confirmed by the measurement results.The three-stage proposed ring VCO was fabricated in the 180-nm CMOS process of SMIC.The measurement results show that the oscillator frequency of the ring VCO is from 0.770 to5.286 GHz and the phase noise is 97.93 dBc/Hz at an offset of 1 MHz from 5.268 GHz with a total power of15.1 mW from a 1.8 V supply while occupying only 0.00175 mm2of the core die area.