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Transmission Phase Calculation for transmission/reflection coefficient request

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

MediaLayerTesting_TransmissionPhase.cfx

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Feko

v2020.1

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Derek Campbell_20514

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

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