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[HELP!] A Basic Question About PHASE SHIFT Measurement in HFSS

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nusjjsun

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Here are the links to my model and my plot:
https://obrazki.elektroda.pl/8319176500_1404602925.jpg
https://obrazki.elektroda.pl/6979615400_1404602926.jpg

Hey guys, I'm totally new to HFSS and now working on a simple coupling microstrip circuit.

The model is quite simple. As the images shown, I want power fed at Port1 of a long microstrip to be coupled to a U-shape resonator and have a 180-degree phase difference between Port3 and Port4. Therefore I make the TOTAL length L of the U-shape resonator half of the wavelength, which is about 200 microns at my working frequency (250 GHz).

But what confuses me is that, no matter how long L (total length of the resonator) is, I always have a 180-degree phase shift between Port3 and Port4!!!

In the attached plot, I make L 1/4 wavelength long. If I plot cang_deg(S(3,4)), or cang_deg(St(3,4)) in my case, I get just 90 degrees between Port3 and Port4. However, what makes sense is cang_deg(S(3,1))-cang_deg(S(4,1)), right? That way, I still have a 180-degree phase shift!

Can anyone help me fix this problem? I really appreciate it!
 

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