Larry,
I do appreciate your distribution of these
citations. I will insert comments for each paper below.
Overall, I think the disagreement boils
down to whether periodic jitter (PJ) is or is not included in bounded
uncorrelated jitter (BUJ). First of all, the division of jitter into unbounded (i.e., RJ), bounded uncorrelated (BUJ) and bounded correlated (i.e., DDJ) is a
perfect taxonomy by the very names of the categories. It guarantees that
all types of jitter are covered and any type belongs to only one category.
I suspect the motivation for measurement
equipment manufacturers in separating periodic jitter before processing the
residue is that spectral peaks are numerically difficult to deal with when
mixed with broad spectral components. But that is no excuse for asserting
that a bounded jitter component
which is uncorrelated to the
signal is not bounded
uncorrelated jitter. I would suggest a new name for BUJ
with the periodic component(s) removed. How about “broad band BUJ”
(BBBUJ – pronounced like BUJ, but with a stutter).
I don’t lightly choose to propose different
terminology than what is in practice, but current practice is simply
self-contradictory. I will attempt to roll this into a rev of T10/07-259.
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of Larry McMillan
Sent: Thursday, May 24, 2007 10:33
AM
To: Alvin.Cox@seagate.com;
t10@t10.org
Subject: SAS PHY teleconference
5/24/07, 10 am CDT: Definition of BUJ and T10/07-259r0
Regarding the discussion in today's phy
call regarding the definition of bounded uncorrelated jitter (BUJ): Here
are a few references I found in just the 1st page of results from a quick web
search. In skimming the various papers/articles I didn't see a single
definition of BUJ that agrees with the definition put forth in
T10/07-259r0. It seems to me the views of the rest of the world need to
be seriously considered before we generate our own variant definition of
BUJ. The links follow. Comments anyone?
Cal Tech Paper differentiates between BUJ
and DDJ:
I
believe this paper and my presentation agree on definitions. I should
probably use the (lately more common) term of DDJ rather than ISI.
BERTScope paper differentiates between BUJ
and other non-ISI DJ:
I like their
figure showing the taxonomy of jitter, except that they do not include PJ &
SJ inside BUJ. The definition of BUJ provided in the paper does seem to
include PJ & SJ, so I guess I have to disagree with that part of their definitions.
|
BUJ: A non-random (bounded) jitter that does not relate
directly to the data signal. Examples include crosstalk, power supply
break-through. In this document the term will be used to refer to the stress
component used to emulate the effects of such signals. This is achieved by
modulation of the data transitions in the time dimension, usually using some
form of PRBS signal.
|
Wavecrest paper differentiates between BUJ
and all other DJ:
Mike
Li, if you’re on this reflector, can you explain why – by the
definitions below – PJ is not part of BUJ?
DCD
is, I think, clearly correlated to the data pattern. It is even more
clearly bounded. So why would it not be BUJ?
Bounded-Uncorrelated Jitter Definition
“Deterministic
jitter that is caused by other than the data on the signal under test.”6
Periodic Jitter (PJ) Definition
PJ can quantify
crosstalk effects from EMI sources. (adjacent lines, power supply noise, etc.)
The last 3
papers seem to follow the lead of the lab equipment manufacturers above in
separating periodic jitter from BUJ.
Guide Tech paper differentiates between
BUJ and PJ:
Guide Tech paper differentiates between
BUJ and and all other DJ:
EE Times Asia article differentiates
between BUJ and other DJ, including PJ:
