SAS PHY teleconference 5/24/07, 10 am CDT: Definition of BUJ and T10/07-259r0
Mike.Jenkins at lsi.com
Fri May 25 09:51:07 PDT 2007
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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 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Larry
Sent: Thursday, May 24, 2007 10:33 AM
To: Alvin.Cox at seagate.com; t10 at t10.org
Subject: SAS PHY teleconference 5/24/07, 10 am CDT: Definition of BUJ
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.
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
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
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