Microwave relay communication realizes long-distance transmission of microwave signals through relay transmission of relay stations. Microwave travels in a straight line and will not be reflected by the atmosphere and ionosphere. Because the surface of the earth is spherical, if microwave communication is carried out on the ground, the antenna must be erected to a certain height, so that there is no object between the transmitting antenna and the receiving antenna, and the two can "see each other". In order to carry out long-distance communication, relay stations (relay stations) should be established at a certain distance in a way similar to relay races. These relay stations are located on tall towers or hilltops, and microwaves are amplified at each relay station before transmission. Microwave relay communication is one of the main means of modern communication, and the other means of communication is satellite communication.

Coaxial cable consists of an insulated inner conductor and an isolated outer cylindrical conductor, which is very suitable for microwave transmission, and the frequency can reach several gigahertz. When transmitting microwaves with higher frequency and greater energy, waveguides should be used. In a waveguide, microwaves pass through in the form of alternating electric and magnetic fields, just as electromagnetic waves alternately transfer energy in the form of electric and magnetic fields in free space.