Standard air-filled rectangular waveguides of dimensions a = 2.29 cm and b = 1.02 cm are designed for radar applications. It is desired that these waveguides operate only in the dominant TE10 mode with the operating frequency at least 25% above the cutoff frequency of the TE10 mode but not higher than 95% of the next higher cutoff frequency. The range of the allowable operating frequency f is

Standard air-filled rectangular waveguides of dimensions a = 2.29 cm a

1.	Standard air-filled rectangular waveguides of dimensions a = 2.29 cm and b = 1.02 cm are designed for radar applications. It is desired that these waveguides operate only in the dominant TE10 mode with the operating frequency at least 25% above the cutoff frequency of the TE10 mode but not higher than 95% of the next higher cutoff frequency. The range of the allowable operating frequency f is
A.	8.19 GHz ≤ f ≤ 13.1 GHz
B.	8.19 GHz ≤ f ≤ 12.45 GHz
C.	6.55 GHz ≤ f ≤ 13.1 GHz
D.	1.64 GHz ≤ f ≤ 10.24 GHz
Answer» C. 6.55 GHz ≤ f ≤ 13.1 GHz