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Multiple ports for finite ground

Question asked by temur on Apr 22, 2019
Latest reply on Apr 24, 2019 by volker_muehlhaus

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Hi There,

I am currently working on a reconfigurable UWB MIMO antenna. I used momentum to run EM simulation for my matching network. I have a finite ground for each antenna and I defined ports for each SMD elements connection points( only for one of the antenna. I used a single port for the other antenna). I labeled the port right after the first antenna as port1 and port 2 for the 2nd antenna. I found out I have different S11 and S22( antennas are identical). Whenever I remove the ports I defined for SMD elements, I get exactly same S11 and S22. I am guessing this is a common(reference) ground problem and I do not know how to solve it. I attached my workspace and I am hoping someone can help me.

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MyWorkspace_wrk.7zads.zip37.2 MB

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volker_muehlhaus Apr 24, 2019 10:30 AM

Hello,

your ground plane pin/port modelling looks good to me.The only detail that I don't like is the ground plane mesh, which is not aligned with the mesh of the signal trace. I recommend to set mesh alignment to "agressive".

Best regards

Volker

Hint: In ADS2017 and later, you no longer need the manually drawn "ground" pins for the minus terminal on "drawn" ground layers. Instead, in the port editor you can now set the ground layer for each port, and ADS will create the negative terminal for you. Very convenient.

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volker_muehlhaus Apr 24, 2019 11:57 AM

I found another issue: you had enabled port calibration, but that doesn't work properly with the pins somewhere inside the pads. It seems that port calibration doesn't detect that unfortunate case, and gives strange results.

In my testcase, I get much more consistent results between both antennas with port calibration disabled (Feed type: Direct).

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temur @ volker_muehlhaus on Apr 24, 2019 1:57 PM

Hi Volker,

Thanks for the explanation. As you mentioned I set mesh alignment to "aggressive" but the result was no different. As you show it might be due to the calibration (Your results look similar to HFSS). By the way, I do not see any "Gnd Layer" and "Feed Type" in my port editor window. I believe 2016 does not have this option or I need to enable it somewhere?

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volker_muehlhaus @ temur on Apr 24, 2019 2:15 PM

Yes, the choice of finite ground layer is a new feature in ADS 2017.

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volker_muehlhaus Apr 24, 2019 10:30 AM
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Hello,

your ground plane pin/port modelling looks good to me.The only detail that I don't like is the ground plane mesh, which is not aligned with the mesh of the signal trace. I recommend to set mesh alignment to "agressive".

Best regards
Volker

Hint: In ADS2017 and later, you no longer need the manually drawn "ground" pins for the minus terminal on "drawn" ground layers. Instead, in the port editor you can now set the ground layer for each port, and ADS will create the negative terminal for you. Very convenient.

1 person found this helpful
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volker_muehlhaus Apr 24, 2019 11:57 AM
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Correct Answer
I found another issue: you had enabled port calibration, but that doesn't work properly with the pins somewhere inside the pads. It seems that port calibration doesn't detect that unfortunate case, and gives strange results.

In my testcase, I get much more consistent results between both antennas with port calibration disabled (Feed type: Direct).

1 person found this helpful
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- temur @ volker_muehlhaus on Apr 24, 2019 1:57 PM
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  Hi Volker,
  
  Thanks for the explanation. As you mentioned I set mesh alignment to "aggressive" but the result was no different. As you show it might be due to the calibration (Your results look similar to HFSS). By the way, I do not see any "Gnd Layer" and "Feed Type" in my port editor window. I believe 2016 does not have this option or I need to enable it somewhere?
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  - volker_muehlhaus @ temur on Apr 24, 2019 2:15 PM
    Mark Correct
    Correct Answer
    Yes, the choice of finite ground layer is a new feature in ADS 2017.
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Multiple ports for finite ground

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