26 December 2023 3 7K Report

Hello,

Here is my simulation regarding the WR90 waveguide dimensions.

The S21 is acceptable and based on the waveguide theory it shows the right answer of cutoff frequency. But the S11 is very strange:

1)why does it get a value less than -100dB for frequency less than 2Ghz?

2)If the waveguide is fully matched at 2Ghz (regarding the S11 value), and based on the value of S21 at 2Ghz, No transmission occurs, so where does the input power go? if it reflects to the input the S11 should be less than -3dB not -120dB, if it transfers all power, but where the power goes.

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