feedantenna

A feed antenna, or antenna feed, is the interface that delivers radio frequency power from a transmitter to an antenna or, in receive mode, takes the captured signal from the antenna to the receiver. It encompasses the feed point, connecting transmission line, impedance matching networks, and often a balun or other signaling transformers. The feed determines how power is transferred into the radiating element and can influence polarization, bandwidth, and overall efficiency.

In single-element antennas, the feed is typically a coaxial or balanced transmission line connected at the feedpoint of the radiating element, such as a dipole or monopole. For parabolic dish antennas, the feed is usually a horn or waveguide structure placed at the dish focus so that the radiation from the feed is reflected into a narrow beam. In antenna arrays, the feed network distributes the input signal among elements with controlled amplitude and phase, using power dividers, phase shifters, and decoupling networks to shape the overall radiation pattern.

Common design considerations include impedance matching to minimize reflections, typically toward 50 ohms or 75 ohms, and ensuring the feed preserves the desired polarization. Losses in the feed, its physical arrangement, and interaction with nearby structures can affect efficiency and pattern. Feed systems may be integrated into the antenna structure or provided as a separate unit, and they must be designed to withstand environmental conditions in outdoor installations.

Examples of feed configurations include coaxial feeds for dipoles, balanced ladder lines for certain dipole arrangements, waveguide-fed horn antennas, and microstrip or stripline feeds for patch antennas and arrays.