Quantifying Jitter - Keysight Technologies N4960A User Manual

Operation Overview
Jitter
Figure 2. Eye closure with low (left) and high level of jitter (right)
2.4.1

Quantifying Jitter

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In serial data systems, excessive jitter acts to "close the eye" which will
eventually result in bit errors, as the bit transition moves closer to the
receiver's decision point time window.
A common test for a serial data receiver is its susceptibility to jitter. The
test is performed by driving a known data pattern into the receiver using
the N4951A/N4951B pattern generator which is stressed with a known
amount of jitter. The received data is compared to an internal reference
pattern of the N4952A error detector, and the number of incorrect
detected bits is counted. By varying the characteristics of the jitter used
to modulate the test data generator, the receiver's performance can be
characterized.
The level or "amplitude" of jitter refers to the instantaneous
displacement in time of the measure point (transition) from its ideal
location. When applied to a stress generator, the amplitude refers to a
level of reoccurring jitter, rather than a single instantaneous edge
displacement. The jitter amplitude will be stated as a peak to peak
displacement, or a root means squared (rms) value, depending on the
nature of the jitter distribution.
Receiver
Decision Point
Keysight N4960A Serial BERT 17 and 32 Gb/s User Guide