Teledyne LeCroy PeRT3 Phoenix System - Manual (Page 60)

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Teledyne LeCroy System Control Ribbon ‐‐ Channel Tabs
Figure 6.17: Emphasis Panel
Random Jitter
The Random Jitter panel allows the user to introduce and control random jitter into the
signal. Random jitter can be low frequency (LF), high frequency (HF), very high frequency
or a combination of the three. The value selected is the root‐mean‐square (RMS) of the
jitter introduced. For the specific range of the 3 Random jitter types, please refer to the
PeRT
3
Phoenix datasheet.
Figure 6.18: Random Jitter Panel
When used in this context, jitter is the variation in pulse position in the time domain. In
an ideal jitter‐free system, each electrical transition would occur at precise intervals
defined by the data rate of the bit stream (e.g., 6 Gb/sec). In practice, there is always
some level of jitter as subsequent pulse edges vary slightly from the ideal, and as this
variation becomes appreciable relative to the length of each pulse, the receiver has more
challenge to correctly determine the value of the bit.
Since random jitter is specified in picoseconds (ps), the degree to which the bit stream is
degraded through the introduction of random jitter will also depend on the data rate. For
a data rate of 1.5 Gb/sec, the width of each bit is 667 ps, so an RMS jitter of 6 ps would
introduce an average variation of approximately 1% of the pulse width (or unit interval).
For a data rate of 6 Gb/sec, the pulse width is 167 ps, and the same 6 ps RMS jitter is an
average variation of approximately 4% of the pulse width (or unit interval).
The random jitter is generated by a physical noise source with a roughly Gaussian
distribution, so while the RMS of the random jitter to 4% of the unit interval, a small
number of transitions will have considerably larger jitter. On average one in a trillion