[SI-LIST] Re: Draft Touchstone 2.0 document available

Patrick,

Thank you for the kind comments and suggestions!

The specification is now being considered by the IBIS Open Forum for
standardization and your request was discussed at our most recent
meeting, this past Friday.  We can certainly consider making this change
in version 2.0 files.  It would not be a difficult adjustment to make to
the draft and would make the format more consistent.

One concern is simply whether changing the order for version 2.0 files
would increase confusion in switching to the new format, particularly
when converting existing files to 2.0 would be convenient.  We tried to
navigate a middle path between making radical improvements in 2.0 and
keeping existing Touchstone files, tools and methods almost unchanged.
In addition to maintaining backward compatibility, we elected to
maintain most of the existing network data format, in order to make the
2.0 transition reasonably easy.  The exception is the removal of
normalization, which was required to support per-port impedances.

So, in your opinion (and in that of the SI-List readers) would
correcting the ordering of S12, S21 in 2.0 files outweigh the resulting
inconsistency with the previous ordering and existing files, tools,
etc.?

Thanks again for your comments, and also thanks to those who provided
comments off-line.  Anyone interested in the topic is certainly welcome
to attend our Open Forum teleconferences and participate in the
Touchstone 2.0 discussions.

- Michael Mirmak
  Intel Corp.
  Chair, IBIS Open Forum

  http://www.eigroup.org/ibis/
  http://www.eda.org/ibis/

-----Original Message-----
From: Zabinski, Patrick [mailto:zabinski.patrick@xxxxxxxx]=20
Sent: Sunday, December 16, 2007 7:33 AM
To: Mirmak, Michael; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Draft Touchstone 2.0 document available

Michael,

Thank you and the IBIS Open Forum for supporting and updating
the Touchstone Spec.  The spec has become a de facto industry
standard, and it is in much need of updating.

Overall, I really like the improvements suggested in Draft Version 2.
They should enhance the utility of the file format and ease
tool development that supports the format.

I spoke with a few folks about the draft, and we would appreciate
consideration of one change.  Under Network Parameter Data, the
ordering of the S-parameter matrix elements are consistent for
most - but not all - matrix sizes.

More specifically, the 1-, 3-, 4-, 5-, ... port matrices are
presented in Ascending-Row then Ascending-Column order, which
matches most (all?) common matrix representations.

In contrast, the 2-port matrix breaks this order, in that S21
(Row 2) is listed before S12 (Row 1). =20

Although we can generally adapt to the 2-port matrices having their
own unique element ordering, it has historically caused many
issues for several of us.  Several analysis and measurement tools
do not follow this ordering, and many engineers are unaware of
the uncommon ordering.

If at all possible, we would much appreciate the 2-port matrix
element ordering to comply with the rest of the spec.  By doing so,
it would make Touchstone format consistent with many
commercially-available
tools and make it easier (i.e., less error prone) for folks to
develop tools around it.

Much appreciate your consideration.

Pat

>=20
>=20
> -----Original Message-----
> From: Mirmak, Michael=3D20
> Sent: Wednesday, December 12, 2007 5:26 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: Draft Touchstone 2.0 document available
>=20
>=20
> The IBIS Open Forum has completed a draft of an improved Touchstone
> specification, entitled Touchstone 2.0, to expand the capabilities of
> the original format and eventually release it as an industry standard.
> Some of the changes in the new version include:
>=20
> - support for independent per-port reference impedances
> - the number of ports that may be represented is unlimited
> - support for lower- or upper-half matrix representations, to reduce
> file size
> - the version number, the number of ports and the number of=20
> frequencies
> in any file have all been made explicit
>=20
> Backward compatibility with 1.0 models has been preserved.
>=20
> Touchstone 2.0 will be formally introduced at this week's IBIS Open
> Forum teleconference, for review and comment in preparation for
> standardization.
>=20
> The latest review draft may be obtained at the URL below.  =20
> Comments are
> welcome.
>=20
> http://www.eda.org/ibis/docs/touchstone2_review_draft.pdf=3D20
>=20
> - Michael Mirmak
>   Intel Corp.=3D20
>   Chair, IBIS Open Forum
>=20
>   http://www.eigroup.org/ibis/
>   http://www.eda.org/ibis/
>=20
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