[SI-LIST] Re: AW: Re: Different Simulation Results
- From: "Ing. Giancarlo Guida" <gianguida@xxxxxxxx>
- To: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- Date: Wed, 17 Mar 2010 13:52:15 -0100
Gert,
this is exactly my point...
I fully agree with your comments.
It is important to have a knowledge about the tool you are using and
about the phenomenon you want model
and it is also essential to recognize that each tool has its own field
of application, limitation, advantages and disadvantages.
Giancarlo
Havermann, Gert ha scritto:
> Giancarlo,
>
> it is not HFSS or SIwave making mistakes, its the user. But on the other
> hand, some tools make it easy to create errors, and some tools prevent
> errors. Therefore it is key to know the tool, and to know what you are doing.
> And even if you think you know what you are doing, verify that you did it
> right.
> Every simulation engine has some simplifications or approximations build in
> to speed up the simulation process (things like limited frequency range, or
> approximations of boundaries, material models with fixed parameters....).
> Knowing those will help to use the tool in the right way.
>
> Two good examples are:
> ADS: if you use the math function to calculate TDR impedance from
> S-Parameters, you have to specify: ref.Imp, time delay, Tstart, Tstop and the
> window function. Many users don't know that the Ref impedance is defined at
> the impedance at Tstart, wich means the plot os forced to the ref.Imp at
> Tstart. If you have S-Parameters of a 110 Ohm trace, refImp is 100 Ohm, and
> Tstart is a positive number, then you will see a flat 100 Ohm TDR plot.
> Chosing a negative number will result in 110 Ohm.
> CST: CST uses different mesh engines. if impedance matters, you must use the
> PBA mesher instead of the FPBA because the latter requires a much finer mesh
> (approx factor 3) for the same acuracy.
>
> For most of the problems (especially a simple trace) you will find a way to
> get the right answer, but as I said, some tools require more work to get
> there.
>
> BR
> Gert
>
>
>
>
>
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>
> Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
> Auftrag von Ing. Giancarlo Guida
> Gesendet: Mittwoch, 17. März 2010 14:41
> An: Istvan Novak
> Cc: Mohamad Haghtalab; si-list@xxxxxxxxxxxxx
> Betreff: [SI-LIST] Re: Different Simulation Results
>
> Hi folks,
> I seriously doubt that software like HFSS and SI wave can make a mistake
> simulating a simple configuration like two coupled parallel microstrip lines.
>
> I would suspect that one of the model have something wrong; I bet that any
> Ansoft AE could easily help on this.
>
> By the way, with HFSS it is possible to simulate a transmission line
> structure of an arbitrary length by modeling a little piece and using the
> deembedding feature, provided that the structure is uniform.
>
> Regards
> Giancarlo
>
>
>
>
> Istvan Novak ha scritto:
>
>> At what frequency do you see this difference, and was the length the
>> same in the two simulators? In SiWave you can easily simulate very
>> long traces, whereas in HFSS your maximum length might be just a few
>> hundred mils.
>>
>> Regards,
>>
>> Istvan Novak
>> Oracle
>>
>>
>> Mohamad Haghtalab wrote:
>>
>>
>>> Hi all
>>>
>>> I've simulated two coupled parallel microstrip lines with both HFSS
>>> and SIwave(from
>>>
>>> Ansoft), there is good agreement between the SHAPE of Scattering
>>> Matrix results in two
>>>
>>> softwares,BUT in the LEVEL of them there is about 15 - 20 dB
>>> difference,what do you
>>>
>>> think about this?
>>>
>>> Regards
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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