[SI-LIST] Re: Spectre S-parameter based modeling- Stability issues
- From: "Zabinski, Patrick" <zabinski.patrick@xxxxxxxx>
- To: <mkeezhve@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sat, 2 Dec 2006 06:20:53 -0600
Madhu,
Enforcing passivity is a good step, but it might not be
enough. You should also consider causality constraints,
which are bit more challenging to enforce.
When you're enforcing passivity or causality, there are
two things to keep in mind:=20
1) the fact that your S-parameter data is not well behaved
(i.e., non-passive, non-causal) suggests that it is likely
incorrect/inaccurate. Minor violations can often be tolerated,
but "minor" is a relative term that is difficult to quantify
in a general sense.
2) When enforcing passivity and causality, you are changing
the data, and thus you are modifying the behavior of the
model. The issue is if you're modifying the file in the
correct/better direction, or are you making the model
worse.
When you get files that have convergence problems, the first
step is to go back to the source to double-check where
the raw S-parameter data file is coming from and do what you
can to make it passive/causal right out of the box.
If that is not possible (most often the case), then the
plan you outline sounds reasonable with the caveats/concerns
I mention above.
You did not mention what other tools you have, but there are
a few commercial tools that enforce passivity and causality
for you. If you have the opportunity, you might consider
trying one of them before creating your own tool.
Pat
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx=20
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of=20
> Madhusudanan K Sampath
> Sent: Friday, December 01, 2006 11:16 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Spectre S-parameter based modeling-=20
> Stability issues
>=20
> Hi All,=20
> I am using n-port component in spectre to perform time domain=20
> simulation
> using touchstone s-parameter files for power planes which are=20
> obtained from
> measurement/full wave tools. In many cases, the simulation=20
> explodes due to
> stability reasons. What are the possible causes of this and=20
> how can one
> solve this issue. I think Spectre n-port component uses=20
> convolution methods
> to perform time domain simulation from frequency domain=20
> s-parameter data and
> hence are prone to convergence issues. If so how does it=20
> enforce passivity
> in the model. I verified the s-parameter matrix for eigenvalues and it
> proves the data is not passive. I would like to compensate=20
> for passivity and
> then re-try the time domain simulation. There are quite a few=20
> interesting
> passivity enforcements techniques in literature by Dr. B.=20
> Gustavsen and Dr
> S.G. Talocia . However they are applied on the rational=20
> functions which are
> obtained by vector fitting the data. My question is if I=20
> vector fit the
> data, enforce the passivity using these techniques and then=20
> calculate the
> S-parameter matrix for each frequency point from the passive rational
> function model. Will spectre give stable results with this=20
> new data ?=20
>=20
> Please share your ideas and views on this. Thanks in advance.=20
>=20
> Madhu=20
>=20
> =20
>=20
>=20
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>=20
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>=20
> List technical documents are available at:
> http://www.si-list.org
>=20
> List archives are viewable at: =20
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
> =20
>=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
