E2681A Datasheet, PDF (4/15 Pages) Keysight Technologies – EZJIT Plus Jitter Analysis Software

04 | Keysight | EZJIT Plus Jitter Analysis Software for Infiniium Oscilloscopes – Data Sheet
Ultimately, this means two problems occur. First, the RJ measurement can be inaccurate.
Second, when measuring Total Jitter (TJ) vs. BER, TJ can be dramatically overestimated
due to the RJ multiplier. For example, TJ = DJ + 14*RJ for a BER of 10^-12. This means
the scope will provide an unfairly negative report of the overall jitter performance of your
serial data link, even tough the real RJ is dramatically less.
To solve the BUJ problem, EZJIT Plus provides two distinct algorithms for RJ extraction
to ensure you achieve accurate measurements under all signal conditions.
The Tail Fit algorithm accurately extracts RJ, even in extreme ABUJ/crosstalk
environments, by fitting directly to the tail of the RJ,PJ histogram.
Figures 3 and 4 contrast the two algorithms in a contrived jitter measurement with
extreme crosstalk. The tail fit algorithm in Figure 4 provides a much better fit to the BER
bathtub curve in the lower left and reports significantly lower RJ and TJ.
Figure 3. Jitter separation with artificially extreme crosstalk using spectral algorithm for RJ extraction.
Notice the discontinuity in the BER bathtub, indicating that the extraction is getting poor convergence.
Figure 4. Jitter separation with the same artificially extreme crosstalk shown in Figure 3 using tail fit
algorithm for RJ extraction. Notice the good fit to the BER bathtub and dramatically lower RJ and TJ results.