How Phase Noise Appears in Oscillators

Abstract

Wireless transceivers closely specify the phase noise in the local oscillator. Yet it is not very well understood how phase noise is predicted, especially in oscillators which do not use a passive resonator. It is also difficult to model flicker noise in the close-in phase noise spectrum. This is a qualitative discussion of the various physical processes responsible for phase noise production, particularly in CMOS oscillators, and it offers a common treatment of resonator-based oscillators, ring oscillators, and relaxation oscillators.