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    EM simulation of 50ohm line

    Hello,

    I am working on EM simulation of transmission lines. For example, a 50ohm transmission line.

    What kind of calibration should I use for the input and output ports? Is there any general rules that specify when to use TML or None? For this 50ohm line I am simulating, None or TML calibration gave different results.

    Click image for larger version. 

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    Thanks!

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  2. #2
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    Re: EM simulation of 50ohm line

    You should use Direct Mode because TRL Mode is used for the Ports which have an Reference Off-Set only.
    For instance, if you move a Port along the Transmission Line with an Off-Set, you can use TRL Mode otherwise Direct Mode.
    Click image for larger version. 

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    Upper example uses Direct Mode, Lower example uses TRL Mode.You see the difference..



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    Re: EM simulation of 50ohm line

    Quote Originally Posted by BigBoss View Post
    You should use Direct Mode because TRL Mode is used for the Ports which have an Reference Off-Set only.
    I don't agree. Without reference plane shift, TRL calibration can remove the (usually small) port discontinuity. Port discontinuity results from feeding at the end of the line with a vertical voltage source between line and ground. This results in local field distortion, compared to the regular line mode.

    Using TRL port calibration is fine for microstrip lines over ground at the bottom of the Momentum substrate.

    Limits: TRL cal standards are created by extending the line behind the scenes. This requires a proper (usually infinite) ground plane under the line. For lines with "drawn" finite ground or RFIC lines over lossy silicon, I switch off port deembedding. TRL cal would results is less accurate results then, so better switch it off for those cases.



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  4. #4
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    Re: EM simulation of 50ohm line

    Quote Originally Posted by volker@muehlhaus View Post
    I don't agree. Without reference plane shift, TRL calibration can remove the (usually small) port discontinuity. Port discontinuity results from feeding at the end of the line with a vertical voltage source between line and ground. This results in local field distortion, compared to the regular line mode.
    Quote Originally Posted by BigBoss View Post

    Upper example uses Direct Mode, Lower example uses TRL Mode.You see the difference..
    Thanks BigBoss and volker@muehlhaus for replying. I kind of get what both of you mean. In my case, I am trying to simulate the transmission line in a matching network (Please see picture). This line connects the inductor and the cap together. So I should skip TRL calibration for the ports right?

    Attachment 149035



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