Jitter and phase noise in oscillators and phase-locked loops

Abstract

This paper presents a unified description of phase noise and timing jitter of oscillators and PLLs based on diffusion theory. Analytical expressions for period jitter, cycle-to-cycle jitter, and absolute jitter are derived and related to the power spectral density of the excess phase and the relative single-sideband phase noise of the oscillator. In addition to white noise sources resulting in phase diffusion, the effects of flicker noise and noise in the control voltages including supply and substrate noise are considered. More specifically, the absolute rms jitter of a PLL is related to the white and the flicker noise of a free-running oscillator. For an experimental 60 GHz oscillator fabricated in a 0.25 μm SiGe:C BiCMOS technology a phase noise of -90 dBc/Hz is measured at 1 MHz offset. From this measurement, an absolute rms jitter contribution of 70 fs is predicted for a 5 MHz bandwidth PLL.