[SI-LIST] Re: Touchstone vs. "txt" file output
- From: "Michael Rose" <mrose@xxxxxxxxxxxx>
- To: "Yuriy Shlepnev" <shlepnev@xxxxxxxxxxxxx>, "Ralph Wilson" <wilson@xxxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 6 Jul 2010 19:22:45 -0400
I had a problem with a CST Touchstone where the lines were not
terminated (i.e. cr/lf) at the proper data record boundaries. The
viewing software would read the first row of data and if split across
multiple lines, would assume the number of ports was based on the number
in that line (not the number in that data group). Maybe you're having
similar boundary problems.
- Mike
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Yuriy Shlepnev
Sent: Tuesday, July 06, 2010 6:56 PM
To: 'Ralph Wilson'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Touchstone vs. "txt" file output
Hi Ralph,
Take a look into the generated Touchstone file - most likely it is
written
in the original Touchstone format that does not support the mixed-mode
S-parameters. Mixed mode requires different normalization impedances for
differential, common and single-ended ports that is supported only by
the
new Touchstone version 2.0.
After reading data from the older Touchstone file with the single-ended
S-parameters, you have to transform them into the mixed-mode to see
SDD11 or
SDD12. Free software Simbeor 2008.01 L0 can help you to do such
transformations and in addition to estimate quality of the computed
S-parameters (passivity, causality, reciprocity, symmetry). The software
is
available at
www.simberian.com/Downloads.php (requires registration).
Best regards,
Yuriy Shlepnev
www.simberian.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of Ralph Wilson
Sent: Tuesday, July 06, 2010 9:49 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Touchstone vs. "txt" file output
All,
I am using CST Microwave Studio for via investigation at high speed
SERDES rates. After
a simulation I am able to view various plots, including "magnitude (dB)"
vs. frequency. If I
export this as a "txt" file and convert it to csv, I can see the same
curves when I plot them in
Excel. However, if I export these same results as a "Touchstone file",
when I open the resulting
.s4p file in a Touchstone viewer many of the curves are different (some
of the S parameters
seem to be very similar, many are significantly different). To the best
of my knowledge, I am
keeping the port(s) and modes(s) straight - at least based on the
documentation provided on
exporting such files. I have also tried to make sure I'm looking at
"magnitude" and not simply
the real / imaginary parts. Based on the way I read the export
documentation, I do not think the
tool is doing a mode conversion.
Is there any reason I should NOT expect these plots to be identical? Is
there any "math magic"
that would manipulate an "SDD21 magnitude in dB" plot (for example) as
it is exported to a
Touchstone file?
Thanks!
Ralph Wilson
Alcatel-Lucent
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