GATE 2026 EC – Question 33
The cutoff frequency (in GHz) for the dominant TE$_{10}$ mode of an air-filled rectangular waveguide of inner dimension $0.28$ inch $\times$ $0.14$ inch is ________. (rounded off to two decimal places)
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Correct answer: 20.98 to 21.20
Explanation
$f_c=c/(2a)$ with $a=0.28\times2.54$ cm $=7.112$ mm. So $f_c=3\times10^8/(2\times7.112\times10^{-3})\approx21.09$ GHz.