[SI-LIST] Re: time domain simulation of s-parameter
- From: <sanjeev_gupta@xxxxxxxxxxx>
- To: <skgupta2005@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 5 Dec 2007 00:58:04 -0700
Hello Sanjeev,
I hope you are using ADS Update 2 or a latter release as there were =
significant enhancements in convolution technology?
If possible, please send us your S-parameter file for us to study and =
provide you an easy solution for the convergence problem you are facing.
Best regards
Sanjeev Gupta
Agilent EEsof
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Sanjeev Gupta
Sent: Tuesday, December 04, 2007 9:36 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: time domain simulation of s-parameter
Thank you all for responding to my query.
Actually no tool is perfect in this world. Each one has its own plus and
minus points.
Power SI is limited with number of ports, As number of ports increases, =
its
a complete mess..
HFSS is good for higher frequencies, but not good for lower freq. so
transient simulation of s-parameter from HFSS is certainly not good.
Q3D is limited to lower frequencies and also on the size of structure.
Ansoft claims that they have the best algorithms to solve such kind of
problems, but they put the condition that one should use all the tools
(HFSS, Q3D, Nexxim) only from ansoft. This seems to me just a marketing
gimmicks.. nothing else..
Now let me come to my problem statement.
I was interested to use ADS for transient simulation after s-parameter
extraction of the signal nets including power plane from Power SI. I =
got my
simulation running after lot of experimentation in convolution tab. my
colleague tried ADS on Power plane related transient simulation after
s-parameter from Power SI. Initially, he extracted power plane model =
till
2GHz, ADS simulation did not converge. Later he extracted till 5Ghz, =
then he
got the simulation going with some changes in convolution tab options.
ADS is able to handle such problems, but we had to lot of manual =
labour.. I
really dont know about the robustness of algo.
Thank you all once again
--Sanjeev
On 12/4/07, Michael Tsuk <mtsuk@xxxxxxxxxx> wrote:
>
> > Hello All
> > I am trying to do time domain simulation using Agilent ADS after =3D
> > extracting s-parameter model from Power SI.
> > But, i am getting lot of convergence issue. Simulation gets =
terminated
> > immediately. I do not get any time domain waveform.
> > kindly suggest a solution.. which tool can solve such problem very
> > efficiently?
> > Thanks in advanve
> > Sanjeev
>
> Sanjeev,
>
> Although I'm not an expert user of either Power SI or ADS, I have some
> suggestions that might help you resolve your difficulty. I've been
> leading
> the research on transient simulation of S-parameters for the Nexxim
> circuit
> simulator team at Ansoft for the past several years. We've had
> significant
> success in creating algorithms for robust transient simulation, and =
the
> work
> has deepened my appreciation for the intricacies of this type of =
problem.
>
> To me, it sounds very much like you have a passivity or causality =
problem
> with the 3D extraction from your EM tool, which is causing the non
> convergence in your transient simulator. You may want to try turning =
on
> passivity enforcement in ADS, and also switching to a non-convolution
> based
> transient algorithm, if that's available. Convolution tends to have
> trouble
> with power-distribution simulations, because interesting things happen
> over
> a wide dynamic range in frequency. Convolution can miss the =
low-frequency
> effects, due to interpolation onto a uniform grid for the inverse FFT.
>
> Adding a DC point if you don't have one is important for high-quality
> transient results, but you'll need to make sure you add a good DC =
point.
> I've seen cases recently where a simple "perfect short" was added, and
> that
> was non-causal and so messed up the transient simulation.
>
> However, there could be passivity or causality problems in the =
original
> Power SI data, which might be causing the non-convergence issue.
> Passivity
> is relatively easy to check (the maximum singular value of the =
S-matrix at
> each frequency must be less than or equal to unity), but causality is
> harder. This brings up one of the advantages of having both EM and
> circuit
> simulation tool coming from the same company: the finger pointing is =
all
> done internally. :-)
>
> Let me know if you have any other questions. Thanks!
>
> --
> Michael Tsuk, Ph.D.
> Ansoft Corporation
> (781) 229-8900, ext. 351
>
>
>
>
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