Tektronix - Understanding and Characterizing Timing Jitter

Our thanks to Tektronix for allowing us to reprint the following article.

Introduction


Timing jitter is the unwelcome companion of all electrical systems that use voltage transitions to represent timing information. Historically, electrical systems have lessened the ill effects of timing jitter (or, simply “jitter”) by employing relatively low signaling rates. As a consequence, jitter-induced errors have been small when compared with the time intervals that they corrupt. The timing margins associated with today’s high-speed serial buses and data links reveal that a tighter control of jitter is needed throughout the system design.


As signaling rates climb above 2 GHz and voltage swings shrink to conserve power, the timing jitter in a system becomes a significant percentage of the signaling interval. Under these circumstances, jitter becomes a fundamental performance limit. Understanding what jitter is, and how to characterize it, is the first step to successfully deploying high-speed systems that dependably meet their performance requirements.


A more thorough definition will be introduced in Section 2, but conceptually, jitter is the deviation of timing edges from their “correct” locations. In a timing-based system, timing jitter is the most obvious and direct form of nonidealness. As a form of noise, jitter must be treated as a random process and characterized in terms of its statistics...


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