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binyaocsu@163.com
Antenna-Theory.com Newbie
Joined: 20 Mar 2019
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 Posted: Thu Apr 25, 2019 8:09 pm Post subject: The limitation of waveguide method to obtain S parameters |
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I am using a rectangular waveguide method to obtain the S11 and S21.
However, I found that the S21 goes large variation when S21 is close to -80dB.
After checking the data in published papers, I think that the waveguide method cannot obtain an extremely low S21. Probably, the lowest S21 it can obtain is around -80dB.
However, the free space method can reach to -100 or -120 dB.
What happens to the waveguide method when S21 is very low?
Why this method cannot obtain the extremely low S21?
Thanks a lot. |
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admin
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| Posted: Thu Apr 25, 2019 10:20 pm Post subject: |
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You're sure it is not a test issue? It looks like the sensitivity is degraded (such as when an LNA is not on and the noise figure is much higher).
I don't know why there would be some physical limitation on dynamic range on one method vs the other. Any notes from the paper that indicate why? |
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binyaocsu@163.com
Antenna-Theory.com Newbie
Joined: 20 Mar 2019
Posts: 5
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| Posted: Fri Apr 26, 2019 3:29 am Post subject: |
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| admin wrote: | You're sure it is not a test issue? It looks like the sensitivity is degraded (such as when an LNA is not on and the noise figure is much higher).
I don't know why there would be some physical limitation on the dynamic range on one method vs the other. Any notes from the paper that indicate why? |
Thanks for your help.
I find that the maximum value of S21 that VNA can provide should be smaller than that of its dynamic range. Theoretically, the VNA's dynamic range is in the range of 100-120 dB.
Thus, I think the S21 cannot reach up to the 90 dB. |
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