[SI-LIST] Re: HSPICE S-paramter questions
- From: Ray Anderson <ray.anderson@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 16 Mar 2005 08:26:58 -0800
Craig-
The way I interpreted Ed's question, I think he was asking about
instabilities (non-convergence, ringing, other simulation artifiacts)
when utilizing the Hspice S element to introduce s-parameter data into a
spice simulation.
I can't comment on the latest release, but in the past I've experienced
"non-intuitive" results using the S element.
One of the reasons there seems to be a proliferation of 3rd party
programs like Sigrity BroadBand Spice, Optimal WideBand Convert, Apsim
SPAR, and many other similar ones from other vendors whose purpose is to
synthesize "black-box" n-port models from s-parameters for use in spice
(including Hspice) is to provide an alternative to the built-in
S-element that has seemed to be problematic especially with large (many
ported) models.
-Ray
Craig Clewell wrote:
>Ed,
>
>I will assume that when you speak of and s parameter model you are talking
>about a Touchstone file.
>
>If this is the case you can import the file into Excel using comma/space
>delimiters and then plot the appropriate s parameter.
>
>Then, you can set up the model by itself in HSPICE and compare the 2 curves.
>This will insure that the s parameter file is not defective. Obviously, if
>you don't get the same result you know that your version of HSPICE is not
>handeling the file correctly.
>
>If you do have a problem in your version of HSPICE a work around may be to use
>discrete components to obtain your ouput as opposed to using the S element. I
>will say that I know the latest version does handle the S paremters correctly
>
>Here is some code that will measure the S11 and S21. Just reverse the input
>and output connections to get the S22 and S12. Also, if you would like to look
>at more than 2 lines you can repeat this code, or put it in a subcircuit so
>that you can wire up as many lines as you wish. This is for a single ended
>configuration. If your application is for differential let me know and I can
>send you the code for the differential configuration if intersted. Don't
>forget to terminate all unused lines in Zo.
>
>*Input node to DUT is 20, and output node to DUT is 28
>*S11 measured from node 8, and S21 measured from node 11
>Rout_BW 28 9 50
>Vin_BW 5 0 AC=1
>Rin_BW 5 20 50
>Vout_BW 9 0 DC=6 AC=0
>E1x 10 0 20 0 2
>V6 10 8 AC=1
>R8 8 0 1e9
>E2x 11 0 28 0 2
>R9 11 0 1e9
>
>Craig
>
>
--
Raymond Anderson
Senior Signal Integrity Staff Engineer
Product Technology Dept.
Package Engineering Group
Xilinx Inc.
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