Data-dependent jitter (DDJ) is a specific class of timing jitter. In particular, it is a form of deterministic jitter which is correlated with the sequence of bits in the data stream. It is also a form of ISI.
Properties
Depending on characteristics of the signal and transmission topology, previously transmitted symbols can affect the edge cross over time. This creates a probability distribution for the timing of the signal edge, which is usually recorded in a PDF.
DDJ's PDF is always a series of pulses at the locations where a specific bit pattern experiences a cross over. Therefore, in order to get an accurate measure of the DDJ in a particular system, a large number of bit patterns must be analyzed (often just a PRBS) unless an analytical solution can be found.
References
"Understanding Jitter Calculations: Why Dj Can Be Less Than DDj (or Pj)". 9 July 2014. Retrieved 21 March 2025. https://www.teledynelecroy.com/doc/understanding-dj-ddj-pj-jitter-calculations ↩
"Data Dependent Jitter VI". www.ni.com. Retrieved 2025-03-21. https://www.ni.com/docs/en-US/bundle/labview-jitter-analysis-toolkit-api-ref/page/lvjitterphtk/data_dependent_jitter.html ↩