Hi folks-
I have been following this thread on the DC point in S-parameters with great
personal interest.
I am looking for a collaborator to explore the importance of an accurate DC
point in S-parameter measurements and system simulations.
Teledyne LeCroy has a new instrument, the WavePulser 40iX, which measures
S-parameters and measures the DC value directly. I am looking for a good
example of an interconnect in which the DC value matters and not having an
accurate value affects the simulated channel performance.
If you have such a channel, I would be interested in working with you to
perform measurements and evaluate the time domain performance- as TDR/TDR
and eye diagram at some data rate. We can use S-parameters with a DC value
and then edit the files to remove the DC value and select a lowest
frequency. We can then compare the simulated channel performance with
various extrapolation methods.
One outcome for this project would be a publication either in DesignCon or
at least in Signal Integrity Journal. If it is suitable, maybe one of the
IEEE trans journals as well. This means the example cant be proprietary.
If you have a channel in which you think the DC performance is important,
and the measurements and simulations can be shared publicly, maybe with some
features hidden, please contact me offline to discuss.
Thanks
Eric bogatin, eric@xxxxxxxxxxxxxxx
*******************************************************
Dr. Eric Bogatin
Signal Integrity Evangelist, Teledyne LeCroy, www.TeledyneLeCroy.com
Dean, Signal Integrity Academy
Technical Editor, Signal Integrity Journal,
Adjunct Prof, ECEE Univ of Colorado, Boulder
707 Windflower Dr
Longmont, CO 80504 USA
cell: 913-424-4333
Twitter @beTheSignal
e: eric@xxxxxxxxxxxxxxx
Signal and Power Integrity- Simplified
Principles of PDN Design- Simplified
******************************************************
-----Original Message-----
From: FreeLists Mailing List Manager <ecartis@xxxxxxxxxxxxx>
Sent: Monday, October 21, 2019 11:08 PM
To: si-list digest users <ecartis@xxxxxxxxxxxxx>
Subject: si-list Digest V19 #223
si-list Digest Mon, 21 Oct 2019 Volume: 19 Issue: 223
In This Issue:
#1: From: Tramp <farhilltramper@xxxxxxxxx>
Subject: [SI-LIST] Re: AW: AW: impact of sparam's DC value
&violation
----------------------------------------------------------------------
Msg: #1 in digest
From: Tramp <farhilltramper@xxxxxxxxx>
Date: Mon, 21 Oct 2019 23:24:59 +0100
Subject: [SI-LIST] Re: AW: AW: impact of sparam's DC value &violations on HS
Hi Gert,
Thanks for the advice. I will definitely try your suggestion.
Cheers,
Tramp
On Thu, Oct 17, 2019 at 2:52 PM Havermann, Gert <Gert.Havermann@xxxxxxxxxxx>
wrote:
Todd,understand what was going on.
it would be great If I would be in the position to demand good
S-Parameters, but the regular way is still that I have to live with
what I get.
Mit freundlichen Gr????en / Kind regards.
Gert Havermann
Signal Integrity Engineer
Dept.: Corporate Technology Services
HARTING Stiftung & Co. KG
Marienwerderstra??e 3
D-32339 Espelkamp
Phone +49 (0)5772 47 857
Fax +49 (0)5772 47 90857
mailto:gert.havermann@xxxxxxxxxxx
http://secure-web.cisco.com/1zb3zaVVBHqZwk5xF_CXIMtLiP7YzhN3DxMQzggVCI
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Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender), Dipl.-Kffr.
Maresa W. M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar Harting,
Dipl.-Hdl. Margrit Harting, Dipl.-Ing. (FH) Dipl.-Wirtsch.-Ing. (FH)
Andreas Conrad, Dr. iur. Michael P??tz Sitz der Gesellschaft:
Espelkamp | Amtsgericht Bad Oeynhausen | HRA 9021 | UST-ld Nr.
DE812136745
-----Urspr??ngliche Nachricht-----
Von: Westerhoff, Todd <Todd_Westerhoff@xxxxxxxxxx>
Gesendet: Donnerstag, 17. Oktober 2019 15:42
An: Havermann, Gert <Gert.Havermann@xxxxxxxxxxx>;
si-list@xxxxxxxxxxxxx
Betreff: RE: [SI-LIST] AW: impact of sparam's DC value &violations on
HS signal performance
Gert,
I think your point gets glossed over often.
Let's look at it this way - most of us would agree that IBIS-AMI
models have portability problems, but how many of us would say that
S-parameters have the same issue? I maintain that they do.
There are a number of aspects to S-parameter portability, but the most
important is probably the DC point. When it's missing, a time-domain
simulator is *forced* to create one and that process is highly tool
dependent. Add the issues associated with obtaining / extracting
accurate low frequency data, and the variance between tools and
results gets even larger.
The fallback - the safety net that we all want to rely on - is that
most tools can "correct S-parameters for missing DC points, passivity,
symmetry and causality". Which sounds great, right? Because how many
of us can really tease those problems out of tabular frequency-domain
data, much less do anything about it? We all want the "Easy" button
that will take bad data and make it good, without out having to really
similar) and then compare.
I maintain that's a trap. Fixing small causality and passivity issues
is fine - *but you need to know the problems were small in the first
place*, such that automated correction is even appropriate. Automated
correction of significantly bad data is just a bad idea.
My point - we should be striving to create (or demand) s-parameter
data with DC points that passes appropriate quality checks. Automated
extrapolation and correction is really just a crutch - for a problem
that shouldn't have existed in the first place.
That's my $0.025 (you get an extra half cent on Thursdays).
Todd.
Todd Westerhoff
High-Speed Design Product Marketing | Electronic Board Systems
300 Nickerson Rd, Marlboro, MA 01752
todd_westerhoff@xxxxxxxxxx | office: 508-303-5821 | cell: 978-846-0203
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Havermann, Gert
Sent: Thursday, October 17, 2019 2:04 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] AW: impact of sparam's DC value &violations on HS
signal performance
Hi Tramp,
the correct DC point is the key to correct domain transformation. If
you need time domain data (like eye or impedance plot) from
S-Parameters then the DC point is very important as it affects the
reference impedance and the causality. Extrapolation works ok if the
extrapolated DC point is still "passive", but especially for
measurements this isn't always the case because VNAs trend to have
problems with the accuracy of the lowest frequency points. That???s
why it sometimes helps for you if you clip below 60MHz.
Just for the fun of it, take a set of S-Parameters and add two
slightly different DC points and compare the results after
transforming it to time domain. And add an "active" DC point (+0.3dB or
And check all those files for causality. You can also transform allhttp://secure-web.cisco.com/1zb3zaVVBHqZwk5xF_CXIMtLiP7YzhN3DxMQzggVCI3ayxgs
these files using the passivity and causality enforcement. This gives
a very nice overview about the importance of the DC point.
Mit freundlichen Gr????en / Kind regards.
Gert Havermann
Signal Integrity Engineer
Dept.: Corporate Technology Services
HARTING Stiftung & Co. KG
Marienwerderstra??e 3
D-32339 Espelkamp
Phone +49 (0)5772 47 857
Fax +49 (0)5772 47 90857
mailto:gert.havermann@xxxxxxxxxxx
http://secure-web.cisco.com/1zb3zaVVBHqZwk5xF_CXIMtLiP7YzhN3DxMQzggVCI
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URSSv4tOQ/http%3A%2F%2Fwww.HARTING.com
----------------------------------------
HARTING Stiftung & Co. KG | Postfach 11 33, 32325 Espelkamp |
HARTING F??hrungsstiftung | Amtsgericht M??nchen | HRA 108479 |
M??nchen
Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender), Dipl.-Kffr.
Maresa W. M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar Harting,
Dipl.-Hdl. Margrit Harting, Dipl.-Ing. (FH) Dipl.-Wirtsch.-Ing. (FH)
Andreas Conrad, Dr. iur. Michael P??tz Sitz der Gesellschaft:
Espelkamp | Amtsgericht Bad Oeynhausen | HRA 9021 | UST-ld Nr.
DE812136745
-----Urspr??ngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> Im
Auftrag von Tramp
Gesendet: Donnerstag, 17. Oktober 2019 00:09
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] impact of sparam's DC value &violations on HS
signal performance
Hi experts,
As we know the DC value of PDN is critical in PI simulations. But for
10Gbps+ SI sim, how much impact an inaccurate DC value of the sparam
10Gbps+ can
produce?
and, quite often we see the extracted sparam has passivity and/or
causality issue at LF and DC, due to extrapolation or other reasons.
So the same question comes again: for 10G+ sim, how much impact on the
eye such violation can pose? Is it ok to simply cut out the part below
60MHz? In my experience for most cases clipping this band of freq
eliminates the majority of passivity and causality violations.
--
Best Regards,
Tramp
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