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Capacitor model differences

Question asked by Leyo on Apr 30, 2014
Latest reply on Jul 7, 2014 by alii
I am finding discrepancies  in the ADS Momentum results with Modelithics capacitor models and S- Parameters.
, I have a copper structure built on RO4350. 
Simulated this in ADS 2102 Momentum  and brought the em model to schematics for co-simulation.
Have four configurations in the schematics  (See the attached)


1.     Using Modelithics ATC 600 S 10 pF cap connected to the copper and the ground plane which is connected through Via. Terminal 1 is used and S11 shows the result.
2.     Used ATC S-parameter in Horizontal configuration for 600S 10 pF. The S parameter file is connected to the ground plane through Via. Terminal 2 is connected and S22 show the result.
3.     Using Modelithics ATC 600 S 10 pF cap connected to the copper and the other end to the ground . Terminal 3 is used and S33 shows the result.
4.     Using  S-Parameter of ATC 600 S 10 pF cap connected to the copper and the other end to the ground . Terminal 4 is used and S44 shows the result.

Results from 1 and 2 are  very different. 3 and 4 matches very well(Please see the attached).  Not sure which is the correct answer here.
The Modelithics model with one terminal connected to the copper and other terminal to ground plane (Connected to real ground through Via) shows a type resonance as evident from S11 plot. But when this models one terminal is connected to ground rather than the ground plane Via combination, the resonance is not there.
Appreciate your help.  

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