Hi,
My research involves the characterization of composite materials. For this, I have performed some measurements using a Vector Analyzer PNA5230A.
The method was the free space using Horn Antenna from 27 GHz to 40 GHz. (see picture). I only measured the S11 parameter for various samples. The S11 parameters of the antenna by itself is presented in the graph.
The variation of the samples in these signals is also presented in the third picture. So now I would like to simulate the same set-up in CST or Ansys. However, I am not sure how to obtain first the curve s11 for the horn antenna. and then with the samples in front obtain the changes.
How can I simulate this same setup?
regards
Sebastian.
The graphs you show are not S11, because S11 cannot be more than 0 dB for a passive component. You need to calibrate properly. Because the reflection from the material is small compared to the reflection of the horn itself you need to use phase and amplitude data so that you can properly subtract the horn response to get the data you need.
The changes are so small that I would be surprised if you can make useful measurements anyway. You seem to be getting almost no reflection from the materials.
You can model the horn in CST with open boundary conditions, with a waveguide port. This will give you S11. Then you can model the material in front of it.
It is unlikely that the S11 you get for the model in CST will be as close to the measured curve as the measurements for the materials are. It is unlikely that the real and simulated results would be this close even if the model was identical to the real horn, which it won't be.
Thank you for your response.
I have performed the calibration with the ECAL kit to port one. Then I connected an adaptor (connector male to a female) and there was the Horn antenna with the waveguide. Could this be the reason for the Gain?
if the change is so small is it because of the method? or the nature of the samples?
I was reading this article and they managed to simulate:
https://www.semanticscholar.org/paper/Free-space-measurement-technique-on-dielectric-of-Wee-Soh/43dce80b0cc442724985889f1485e44785690212
What do you recommend as the best method to simulate the experiments?
Regards
Sebastian
I cannot tell what is happening to make the results wrong, but you can check them initially by just taking the horn off and seeing if S11 is 0 dB, which it should be. Then try putting a metal plate where the material samples are and see what the result is - this is a good thing to compare the results with.
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