Systematic Jitter in a Chain of Digital Regenerators

Abstract

Digital pattern variations are a major source of timing jitter in self-timed digital regenerators. In a chain of similar regenerators, the same jitter is introduced at each one. Therefore, the jitter accumulates systematically. A model is introduced to predict the accumulation of jitter in a chain of identical regenerators with single tuned timing filters. Simple expressions have been derived from the model for the response of the timing phase to sudden pattern transitions and to random patterns. These results show that the jitter grows without bound in a long chain, but its form is such that the tendency to cause errors will not increase as the chain becomes longer. Measurements on a chain of 84 regenerators in a field installation are in excellent agreement with the theory.