A waveguide is a device used primarily in the conduction and transmission of microwaves. It is a hollow tube or pipe that takes the place of wire or coaxial cable to transmit a microwave signal a certain, usually short, distance. Because of the nature of microwaves, an efficient waveguide can carry more than 100,000 transmissions simultaneously.

It did not take scientists long to realize that simple cables were excellent for transmitting radio signals, but were inefficient in the transmission of high frequency signals. They had experimented with several tube-design conductors, finding that they, too, were impractical--unless the frequency of the signal was very high, much higher than any radio waves. As their knowledge of microwaves increased, scientists realized that pipe-design conductors were ideal for microwave transmission.

A waveguide can actually be a dielectric rod as well as a tube conduit, but the latter is used more frequently. Usually made...