Phase Noise Calculation in CMOS Single-Ended Ring Oscillators

All oscillators are periodically time varying systems, so to accurate thephase noise calculation and simulation, time varying model should be considered. The phase noise is an important characteristic of theoscillator design and isdefined as the spectral density of the oscillator spectrum at an offset from the center frequency of the oscillator relative to the power of the oscillator. The linear time invariant (LTI) and thelinear time variant (LTV) models for calculating phase noise in ring oscillator arediscussed. In this paper a new technique based on theLTV model for impulse sensitivity function (ISF) calculation and the phase noise estimation in CMOS single-ended ring oscillator are presented. This method is simpler than theother methods and theISF can be simulated and calculated easily. There is goodmatch between the theoryand the simulation results obtained by this study. The simulation results match the theory well..