[SI-LIST] Re: Ansoft Q2D and Swept Impedance Parameters
- From: "Anil Pannikkat" <APANNIKK@xxxxxxxxxx>
- To: <dowhite@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 11 Dec 2003 11:50:31 -0800
Doug
Reducing the error % has sometimes worked for me in addition to
increasing the number of iterations. I have tried manual meshing also
which did not work. Ultimately when faced with this, I had to decrease
the frequency range or reduce the number of conductors in the model to
keep the same frequency range. (I was told by Ansoft that it is having
difficulty converging all the conductors at the same time).
Regards
Anil
Anil Pannikkat
MTS Package Development * : 408-544-7542
Altera Corporation Fax: 408-544-6404
101, Innovation Drive, M/S 4202 *: apannikk@xxxxxxxxxx
San Jose, CA 95134 *: http://www.altera.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Doug White
Sent: Thursday, December 11, 2003 8:39 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Ansoft Q2D and Swept Impedance Parameters
All,
I have been using Ansoft Q2D to generate tabular w-element models for
lossy striplines. The geometries are fairly typical of what you might
see on a high-speed differential pair for a serial link on a backplane.
I'm doing an impedance-sweep up to 20GHz. For certain geometries, the
frequency-dependent resistance is incorrect. What I'm seeing when I
plot R(f) is that above some frequency, say 1GHz, the impedance curve
begins to "flatten out", and no longer follows the sqrt(f) relationship.
The flattening is quite significant. Now, for a subset of these
problematic geometries, increasing the=20
# of iterations in the sweep mitigates the problem. For the others, it
appears that nothing can be done in the solution setup. Ansoft is aware
of the problem (they say that it is a numerical one), but have not
prioritized its resolution. There are some non-ideal workarounds such
as cutting the data off below some frequency and extrapolating from
there...but I was wondering if any of you have seen this problem and if
so, have you determined an effective solution?
=20
Thanks,
=20
Doug White
Cisco Systems=20
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=20
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