A waveguide is a hollow metallic structure used to transfer high-frequency electromagnetic waves (usually in the microwave range) from one place to another. A waveguide with a circular cross-section is known as a circular waveguide. The circular waveguide supports both TE (transverse electric) and TM (transverse magnetic) modes. In a circular waveguide, TE11 mode is the dominant mode, i.e., at this mode, the electromagnetic wave propagates via the circular waveguide with a minimum loss or minimum degradation. Circular waveguides will only carry or propagate signals above a certain frequency, called the cut-off frequency. The cut-off frequency of the waveguide is inversely proportional to its radius.
They are easier to manufacture and implement than rectangular waveguides since only one dimension, the radius is needed to be maintained. They are used in radio frequency equipment that requires rotation such as a rotary joint in a radar antenna.
fc = Circular waveguide for cut off frequency
c = Speed of light = 3*108 m/s
r = Radius of waveguide
“Circular waveguide of cut off frequency(Fc) is equals to 1.8412 product of speed of light(c) is reciprocal of 6.28 of radius waveguide”
let’s calculate circular waveguide for cut off frequency by circular waveguide. Consider radius as 30 inches