Transmission Phase Calculation for transmission/reflection coefficient request

Lucas_22461
Lucas_22461 Altair Community Member
edited February 2021 in Community Q&A

I am wanting to see the s parameters, magnitude and phase, through an arbitrary media.  I am currently using multilayer green's function, with free space vacuum on either side and my media of interest as a layer in between.  No ground planes.  I have a plane wave source for excitation.  The request is transmission/reflection.  (Ideally I want s-parameters, but a port is required and the plane wave source does not register as a port to my knowledge.)  If I view the reflection and transmission magnitudes over a large frequency band they match exactly to simulations in 2 other notable EM software programs.  The S11 phase then matches for FEKO and the other two as well.  

My issue is the transmission phase.  How is this calculated?  I get agreement for S21 phase for the other 2 softwares, but transmission phase in feko does not give correct results.  If I change the distance that the plane wave travels through vacuum, the phase should change.  However, in FEKO the transmission phase does not change.  I tried changing the phase reference plane of the transmission/reflection request but again the transmission phase does not change whereas the reflection phase does.

Attached is a file for testing.  Can run with the added free space layers once, then run again with the layers removed.  

Please let me know how I can observe the transmission (ideally S21 or S12) phase change through the media.  Perhaps a different request would be better?  

 

Thanks for your help,

Lucas

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Answers

  • Derek Campbell_20514
    Derek Campbell_20514 New Altair Community Member
    edited February 2021

    Hi Lucas:

    There should be no spreading loss from a plane wave and no diffractions from an infinite slab of dielectric material. Monitoring near-fields above and below the surface our material should therefore provide data similar to what is needed for S-Parameters. Users can specify the origin of the Plane Wave source, which helps provide a phase reference for the incident wave. Users can also request near-fields below the dielectric material to monitor magnitude / phase of the transmitted field. The ratio of these two complex numbers should help you.

    Regards,

    Derek

  • Lucas_22461
    Lucas_22461 Altair Community Member
    edited February 2021
    Derek Campbell_21098 said:

    Hi Lucas:

    There should be no spreading loss from a plane wave and no diffractions from an infinite slab of dielectric material. Monitoring near-fields above and below the surface our material should therefore provide data similar to what is needed for S-Parameters. Users can specify the origin of the Plane Wave source, which helps provide a phase reference for the incident wave. Users can also request near-fields below the dielectric material to monitor magnitude / phase of the transmitted field. The ratio of these two complex numbers should help you.

    Regards,

    Derek

    Hi Derek,

    This was helpful, the near-field requests worked and I was able to get the phase through my infinite slab.  There is a matter of a 180 degree phase difference, but that is consistent so I just added 180 degrees to the plane wave source.  Although, why did the transmission request phase not work for this scenario?

    Thank you,

    Lucas

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