[SI-LIST] Re: Using S-parameter file for SI Simulations
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: maxsidhu@xxxxxxxxx
- Date: Thu, 15 Nov 2012 09:04:07 -0500
Hi Siddharth,
A basic rule in SI modeling that we should not cut a structure at a
discontinuity and model the two halves and expect that
concatenating the two models will give us the correct picture
of the whole. With small discontinuities the error may not be
devastating, but with the DC blocking capacitor the capacitor-pad
to capacitor-terminal joint is a significant discontinuity. Also,
unless you have the capacitor's S parameter file created with your
board stackup and geometry, the model has no way of knowing
what is the mutual term between the capacitor's self inductance
and the underlying plane structure in your board. This is true
for both signal-integrity and power-integrity simulations.
Unless you make sure that your design can safely ignore these
differences, it is better to create a model with the capacitor on
the pads and cut the model a little further away where the
discontinuity is not that severe. As Scott pointed out, this is
doable; of course not with all the capacitor plates modeled
individually, so you will need to make some simplifications.
Regards,
Istvan Novak
Oracle
On 11/15/2012 7:01 AM, Siddharth Rajagopalan wrote:
> hi all,
> Please correct me, if this is not the right way to do,
> 1. Model the capacitor pads of appropriate size with ports
> assigned to them using any 2D field solver (Eg: ADS)
> 2. Export the Touchstone file to the circuit simulator in
> ADS and assign the capacitor touchstone file to it.
> PS: if you want to see the effect of cut out effect underneath the
> capacitor, kindly do the same using ADS momentum window.
>
> Siddharth
> Cisco Systems
>
>
>
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