2 Deterministic Jitter

Deterministic jitter is sometimes referred to as bounded jitter. If all components of a system are known, then you can accurately predict how much jitter will be observed at each transitional edge. Because deterministic jitter is composed of all other non-random forms of jitter, it does not follow a general distribution function. There is a finite amount of non-random jitter sources and, therefore, we can deduce that it has a PDF that is bounded. This allows us to characterize deterministic jitter by its peak-to-peak value (a quantifiable value).

Deterministic jitter can be further broken down into two subcategories: Periodic Jitter and Data-Dependent Jitter. Periodic jitter includes any jitter at a fixed frequency or period. It is easy to measure accurately and appears in the frequency spectrum as distinct peaks. Some good examples of periodic jitter are power supply noise and crosstalk from neighboring data lines. Data-dependent jitter encompasses all jitter whose magnitude is affected by changes in a signal’s duty cycle or clock edges. For example, in a data stream the transition between a 0 and 1 of alternating bits (01010101) is going to be different compared to a transition that follows a long string of identical bits (00011001). As this type of behavior is not present in clocks and oscillators, this form of deterministic jitter is considered a non-factor.

There are many ways to categorize jitter and, while it is important to understand what type of jitter you are observing, it is equally as important to be able to measure the different types of jitter. By being able to accurately measure jitter, efforts can be made to filter or remove it and reduce the overall Bit Error Rate (BER) of a system.