[802.3_100GCU] measuring odd-even jitter
guys,
All of the standard PRBS patterns have odd lengths. If the pattern
twice, every possible transition will occur twice, once as an even
numbered transition once as an odd numbered transition. If you measure
the average jitter (deviation from some ideal, equally spaced transition
time) on all even numbered transitions and the average jitter on all odd
numbered transitions the difference, divided by 2, will be the odd-even
jitter. On average the odd and even transitions will suffer the same
ISI shift and error due to improperly chosen threshold so the difference
will be free from these effects. This gives a very clean way of
measuring odd-even jitter.
One error will occur if there is substantial loss at Nyquist due to
the mystically named "phase noise amplification", which will expand
(amplify) odd-even jitter but it will not create it.
charles
--
|--------------------------------------------------------------------|
| Charles Moore
| Avago Technologies
| APD
| charles.moore@xxxxxxxxxxxxx
| (970) 288-4561
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