Dear All,
I have 2 full 2port s-parameters in 30mm waveguide section.
1. 30mm with air
2. 25mm with air and 5mm with material
And I want to extract the s-parameter of 5mm material from the above data.
I think that "de-embedding S-parameter" is solution.
But I don't know how to solve it.
Please give me a hint or calculate the solution.
Thank you very much!
Donghan Lee You may want to read my introductory article "De-embedding & Embedding S-Parameter Networks" in Linkedin.
Maybe you could try first to do a de embedding exercise on a coax structure (in a way like VNA calibration with open short load standards and then go to the waveguide method. One "catch" in particular with the waveguide method are evanescent field from higher order modes in particular for your type of structure (5 mm material near the port)
What do you mean when you say you want the S-parameter of the 5 mm material?
Do you mean you want to know what the S-parameter is for reflection from the boundary between the air and the material, or do you want the S-parameter at the front face of a 5 mm slab of material with air on both sides? Or do you mean something else?
About the only kind of de-embedding I can see you can do here is either:
1)
to unwind S11 by 5 mm by using the properties of the dielectric to calculate the guide wavelength and so the phase length to the material boundary, and rotating the S11 by this much (times 2) to get the S11 of the boundary at the boundary. If you know the loss of the material you can also increase the magnitude of the S11 as you do this. If you don't know the material properties you can't do this.
2)
You can, however, unwind S22 because you know the properties of the air filled waveguide, and can get the guide wavelength and wavenumber, and attenuation if it is significant. Then you have beta and alpha for the air-filled waveguide and the new S11' = S11 * exp((j beta + alpha ) * 25 mm * 2). This is the reflection coefficient from the dielectric boundary at the boundary.
There will be no extra modes generated because the shape of any incident mode in air will be the same as the shape of a transmitted mode in the dielectric, so there is mode-to-mode correspondence.
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