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FEM Simulation of Thin Film Cap

Question asked by mojtaba77 on Nov 19, 2015
Latest reply on Nov 20, 2015 by volker_muehlhaus

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Hi, I am trying to simulate a cap, one port and two ports simulation using FEM in ADS but I got a very different results. Please see the following figures for simulation 1 and and 2. I was wondering if you know which one is accurate and what I am doing wrong here.

Thanks and regards,

Mojtaba

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volker_muehlhaus Nov 19, 2015 11:53 PM
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It is difficult to see the port details in the first example.

Obviously, with your small device under test and the much larger ports, you need to be VERY careful with port de-embedding, and the path length for ground return current. So the second example looks bad to me, with return current having to flow all around the simulation box from port 1 to port 2. You would better place one lumped port between the two plates.
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- mojtaba77 @ volker_muehlhaus on Nov 20, 2015 6:13 AM
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  Thanks Volker,
  
  I attached more zoomed version of first example. The second one results also does not seem correct but I need a two ports results for my cosim simulation. For port calibration I have used None.
  
  Thanks and regards,
  
  Mojtaba
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  - 3D_1port_fig3.png2.1 KB
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  - volker_muehlhaus @ mojtaba77 on Nov 20, 2015 7:08 AM
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    > For port calibration I have used None.
    
    This will give terrible results with FEM for your case. All the port length included as parasitics. Not useful here!
    
    > The second one results also does not seem correct but I need a two ports results for my cosim simulation.
    
    No, you can't create useful 2-port data unless you have a well defined (physical meaningful) ground in the model. What you are looking for is a model with pure series elements. That can be created with a 1-port simulation where you connect the (+) pin to one plate and the (-) pin to the other plate.
    Group the two pins into one differential port in the port editor.
    
    Then in the *symbol* you then need access to both (+) terminal and also the reference terminal. ADS allows you to create the reference pin in the symbol, and here you need that.
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FEM Simulation of Thin Film Cap

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