Design and analysis of 3 stage ring oscillator based on MOS capacitance for wireless applications

This paper comprises the study and performance analysis of switched capacitor ring voltage controlled oscillator (VCO) which uses the method of controlling capacitance to regulate oscillation frequency. In this paper, three stage ring oscillator is designed based on added MOS capacitor in the output of each delay cell. 90 nm CMOS process technology has been used in simulation with the supply voltage of 1.8 V whereas the variation of control voltage differs from 0 V to 0.6 V. A linear tuning characteristic has been achieved ranging from 4.52 GHz to 6.02 GHz in pursuit of wireless applications, specifically for IEEE 802.11a standard. The circuit shows very stable output waveform in different parameters with very low power consumption of 0.295 mW. The figure of merit (FoM) is -155.5 dBc/Hz and the phase noise is very reasonable considering the higher oscillation frequency of the circuit.