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Using 3+ port datafiles in Touchstone or Sdata format

Question asked by JERRY_MARKETOS on Apr 13, 2006
Latest reply on Jan 8, 2009 by mwebber
Using 3+ port datafiles in Touchstone columnar order
and S-Parameter columnar order with Genesys
version 2004.07 and earlier.

See also post which covers version 2005.11 and later
https://edasupportweb.soco.agilent.com/pls/portal/support.show_topic?id=2301

I'm known for being a bit long winded.
This topic is fairly deep (though not too complicated)
You may want to print this and grab a cup of coffee...

This forum cuts posts after a certain predetermined
length.  Information cut off in this initial post
will be continued as the first reply.

More detailed information on the specific makeup of
(S-parameter columnar format) datafiles can be found
by searching Genesys HELP for   data file    and reading
the list topic titled "Creating New Linear Data Files"

S-parameter datafile columnar order is:  (3port example here)
S11  S21  S31  S12  S22  S32  S13  S23  S33

Touchstone datafile columnar order is:  (3port example here)
S11  S12  S13  S21  S22  S23  S31  S32  S33

When using a datafile, if the actual columnar order of the data
is different from that assumed by the entity interpreting
the data, reversal occurs and some of the terms become backward.
(the common terms S11 S22 S33 remain same because the
reference remains identical when reversed.)

Data files can be used by Genesys via different means:

Using data block on schematic-
From linear components menu, place an N-port datablock and browse to file.
(assumption is data in the data file is S-parameter column format)

From just about any component on schematic-
Doubleclick the component to open its properties dialogue,
then switch to the "simulation" tab and choose the radio
button for "use (n) port..." and browse to the datafile.
(assumption is data in the data file is S-parameter column format)

Add a link to data file under "Analysis" on the folder tree.
This is where you can use the dropdown menu for "file type"
to switch whether Genesys interprets the file as S-parameter data
type or Touchstone data type.  (Difference is the columnar order)

Using the link to datafile approach, it is possible to start with
a datafile that has its columns in the Touchstone ordering and
end up with a new datafile with its columns in the S-para order
by doing the following:

In a Genesys workspace, use the link to datafile feature and
set filetype so it reads the Touchstone datafile as intended.
Quick reality check can be made by adding a linear analysis and
viewing an output within Genesys, viewing the S-parameters
to make sure they are as expected.

Then select main menu File, Export, S-Data  and choose a filename
and destination.  The output file will have its columns in
S-parameter data order (not Touchstone order like the source file).

Important note to consider when doing the above-
When dealing with data files, the specific frequency points in the
data file need not be exactly same as the frequency points in the
Genesys linear sweep-  Genesys will interpolate as necessary.
However....
Frequency points in the linear sweep should be chosen so as not
to grossly oversample the data density in a given data file, AND...
if doing the above described process to convert a datafile of
Touchstone column order to a datafile of S-parameter column order,
I strongly recommend taking a few minutes to set the linear sweep
frequencies and number of points etc. so the resulting frequencies
in the linear sweep match exactly the frequencies in the data file
being converted, in the interest of data integrity.  This is often
pretty easy.  Another note-  A great way to force the linear analysis
to reveal exactly what frequencies it's sweeping is to add an output
data table (not a graph) that displays a measurement from the
linear analysis.  

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