A feed line is a line used in wireless communication systems that connects the antenna to the receiver, transmitter, or transceiver. The feed line is used to transmit radio frequency from the antenna to the receiver or from a transmitter to the antenna. Feed lines can be coaxial cables, balanced antenna cables with parallel conductors, or waveguides
.Coaxial cables are most commonly used for feed lines. In these cables, the signal-carrying conductor is arranged centrally and surrounded by a coaxially arranged shield. This prevents the coaxial cable from emitting electromagnetic fields or interfering radiation into the high-frequency cable
.In balanced cables, the two signal-carrying wires are in parallel and are subjected to RF signals in phase opposition
The signal levels are the same at each cable position, but are in phase opposition, which means that the electromagnetic fields of the two wires compensate for each other.
At high frequencies of well over 1 GHz, waveguides are also used as feed lines. With these transmission media, the electromagnetic field moves inside the waveguide. The metal structure prevents the electromagnetic fields from escaping from the waveguide and interfering RF radiation from entering.