User guide

Green points (BER below limit) and red crosses (BER above limit) are used to
display the results.
After a measurement has exceeded the target BER or when moving to the next
frequency point, a measurement settling or relax time can be applied. This allows
the DUT to settle after changes and before the next measurement; this is important
because some devices may need time to recover from error conditions caused by
jitter exceeding the margin during the search for the threshold.
The maximum jitter amplitude the Serial BERT can generate is also frequency
dependent, as illustrated below.
Sinusoidal jitter (SJ) and periodic jitter (PJ) with sinusoidal characteristic are used
for the test. Whether SJ or PJ is used depends on the jitter frequency. SJ supports
wide amplitude variations up to some MHz. PJ supports narrow amplitude
variations over a wide frequency range. The measurement switches automatically
between the two sources.
8 Jitter Tolerance Tests
434 Agilent J-BERT N4903B High-Performance Serial BERT