A waveguide is an electromagnetic feed line that is used for high frequency signals. Waveguides conduct microwave energy at lower loss than coaxial cables and are used in microwave communications, radars and other high frequency applications.
The waveguide must have a certain minimum cross section, relative to the wavelength of the signal to function properly. If wavelength of the signal is too long (Frequency is too low) when compared to the cross section of the waveguide, the electromagnetic fields cannot propagate. The lowest frequency range at which a waveguide will operate is where the cross section is large enough to fit one complete wavelength of the signal.
Geometrically speaking there are three types of waveguides – Rectangular Waveguides, Double Rigid Waveguides and Circular Waveguides. The tables below will give you details on the various waveguide sizes and their properties.
Article From:
https://www.everythingrf.com/tech-resources/waveguides-sizes
