Clock Jitter Estimation based on PM Noise Measurements∗ by

ABSTRACT- “Jitter ” is the noise modulation due to random time shifts on an otherwise ideal, or per-fectly on-time, signal transition. In the absence of ultra-high-speed jitter analyzers, spectrum analysis is an alternate noise measurement for timing jitter. Conventionally, jitter has been defined as a the in-tegral of the phase noise. This paper presents a modified way of calculating timing jitter using phase-modulation (PM) noise measurements of high-speed digital clocks, which considers the frequency response of the jitter analyzer, providing a more accurate map. Measurements of phase noise are typically much more sensitive to phase (or time) fluctuations than a jitter analyzer. A summary table is provided for mapping the results of these measurements in the Fourier fre-quency domain to jitter in the τ domain for various random (specifically, power-law) noise types, spurs, vibration, and power-supply ripple. In general, one cannot unambiguously map back, that is, translate from jitter measurements to phase noise. 1