A 6 cm x 4 cm rectangular wave guide is filled with dielectric of refr...
A 6 cm x 4 cm rectangular wave guide is filled with dielectric of refr...
To determine the range of frequencies over which single mode operation will occur in a rectangular waveguide filled with a dielectric, we can use the cutoff frequency formula. The cutoff frequency is the frequency below which the waveguide can support only one mode of propagation.
The cutoff frequency for the dominant mode in a rectangular waveguide is given by the formula:
fc = (c/2π) * sqrt((m/a)^2 + (n/b)^2)
Where:
- fc is the cutoff frequency
- c is the speed of light in a vacuum (3 x 10^8 m/s)
- m and n are the mode numbers (m is the number of half-wavelength variations along the x-axis, and n is the number of half-wavelength variations along the y-axis)
- a and b are the dimensions of the waveguide cross-section (in this case, a = 6 cm and b = 4 cm)
To determine the range of frequencies over which single mode operation will occur, we need to find the cutoff frequency for the next higher mode (m+1, n) and the next higher mode (m, n+1). The range of frequencies between these two cutoff frequencies will be the range for single mode operation.
Calculation:
- For the dominant mode (m=1, n=0):
- fc1 = (c/2π) * sqrt((1/6)^2 + (0/4)^2) = 1.92 GHz
- For the next higher mode (m=2, n=0):
- fc2 = (c/2π) * sqrt((2/6)^2 + (0/4)^2) = 3.84 GHz
- For the next higher mode (m=1, n=1):
- fc3 = (c/2π) * sqrt((1/6)^2 + (1/4)^2) = 4.32 GHz
Therefore, the range of frequencies over which single mode operation will occur is 1.92 GHz to 4.32 GHz.
Since option 'A' (2.24 GHz to 3.33 GHz) falls within this range, it is the correct answer.