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Ports in Momentum: SMD vs TML

Question asked by circuit_maker on Feb 21, 2017
Latest reply on Mar 14, 2017 by circuit_maker

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Hi,

I am trying to simulate a structure as below:

I have to attach an SMD diode between ports, P1 and P2. I have SPICE model for the diode and C2 and L2 model the package, whereas L3 is for DC path. Separtion between P1 and P2 is 45mils whereas the pad size is 80mil/40mil.

Now, If I define port P1 and P2 as TML, the EM cosimulated results are way too different than the schematic simulation results. However, if I define them as SMD ports, the results are good and only differs little from the Schematic simulation results.

I am not sure which results to believe. I watched a video from ADS channel and I think I should go with the SMD port calibration. Could you please comment on this.

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Mansour001 Feb 22, 2017 9:28 PM

Hello,

I think the problem of unmatched results is due to the distance between the two ports P1, P2 The typical distance should be less than lambda/10 (at the highest frequency). If the distance has not been fulfilled so the current injected has a phase shift and this cause delay through inductor and capacitor.

So try to use an area port and assign the port inside, you can check the ports assignment within ADS documentation Tutorails

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circuit_maker @ Mansour001 on Feb 26, 2017 10:59 PM

Hi Mansour

Thanks for the response. There was some problem in grounding during the layout and that was causing the problem.

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volker_muehlhaus Mar 13, 2017 3:31 AM

Hello,

this is a common misunderstanding of Momentum SMD port calibration, when to use it and what the limitations are. Based on your post here, I have created a simplified version of my global-ground-vs-differential-ground appnote, to show why you can't use SMD ports for this configuration:

Dr. Mühlhaus Consulting & Software GmbH » ADS Momentum: SMD Port Calibration

I hope it's ok to use your circuit example in my appnote introduction. If you want to have it removed, please let me know!

Best regards

Volker

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circuit_maker @ volker_muehlhaus on Mar 14, 2017 10:12 AM

Yet another great appnote from you, Dr Volker. Thank you for clarification.

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4 Replies

Mansour001 Feb 22, 2017 9:28 PM
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Hello,

I think the problem of unmatched results is due to the distance between the two ports P1, P2 The typical distance should be less than lambda/10 (at the highest frequency). If the distance has not been fulfilled so the current injected has a phase shift and this cause delay through inductor and capacitor.
So try to use an area port and assign the port inside, you can check the ports assignment within ADS documentation Tutorails
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- circuit_maker @ Mansour001 on Feb 26, 2017 10:59 PM
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  Hi Mansour
  
  Thanks for the response. There was some problem in grounding during the layout and that was causing the problem.
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volker_muehlhaus Mar 13, 2017 3:31 AM
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Hello,

this is a common misunderstanding of Momentum SMD port calibration, when to use it and what the limitations are. Based on your post here, I have created a simplified version of my global-ground-vs-differential-ground appnote, to show why you can't use SMD ports for this configuration:
Dr. Mühlhaus Consulting & Software GmbH » ADS Momentum: SMD Port Calibration

I hope it's ok to use your circuit example in my appnote introduction. If you want to have it removed, please let me know!

Best regards
Volker
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- circuit_maker @ volker_muehlhaus on Mar 14, 2017 10:12 AM
  Mark Correct
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  Yet another great appnote from you, Dr Volker. Thank you for clarification.
  Like • Show 0 Likes0
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Ports in Momentum: SMD vs TML

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