What are Circular Waveguides?

A waveguide is a hollow metal tube (rectangular or circular in cross section) that transmits electromagnetic energy from one place to another. A waveguide with a circular cross-section is called as Circular Waveguide. It supports both transverse electric (TE) and transverse magnetic (TM) modes. TE11 is the dominant mode in a circular waveguide i.e., a signal in this mode propagates with the minimum degradation. 

The circular waveguide is easier to manufacture than rectangular waveguides and is relatively easy to install. It is usually used to connect a horn antenna with a reflector in tracking radars and for long-distance waveguide transmission above 10 GHz.

The cut-off frequency of a circular waveguide is inversely proportional to its radius. See the formula below - r is the radius of the circular waveguide and C is the speed of light. Use the circular waveguide cutoff frequency calculator if you need to calculate this.

Based on frequency bands, there are fixed waveguide sizes for circular waveguides. Click here to see the circular waveguide sizes.