On Fri, 14 Jan 2011 09:57:44 -0500, "Arny Krueger"
wrote:

"Don Pearce" wrote in message


And of course the term jitter is used with cables -
wrongly in my view. Jitter is a random perturbation of
the data edges caused by noise events. The inaccuracies
caused by cables are systematic and identical on each
data edge. This means that they can be corrected. Either
matching the cable better or using channel estimation
(all mobile phones have this and it is dirt cheap) to
measure and cancel the inaccuracies that shift the edges
out of place.

The digital signal's edges tend to wander around because the cable is
ultimately a low pass filter and the spectral content of the digital data
passing through the cable varies as the data varies. So matching the cable
better can't be of much help.

No, this simply isn't so. Matching a cable properly results in a flat
frequency response and a flat group delay. This reshapes the signal
perfectly.

That leaves the more complex methods like channel estimation or buffering
and reclocking.


More complex, sure, but not exactly taxing these days.

d