feedhorn

A feedhorn, or horn antenna, is a microwave antenna that serves as the feed for a parabolic reflector or other high-frequency antenna. It converts the guided mode from a waveguide or coaxial feed into a directed free-space beam, while providing impedance matching and polarization control. The feedhorn defines the phase center of the antenna and helps shape the beam before it reaches the dish.

Common shapes are conical and pyramidal horns; corrugated horns use thin ring corrugations to achieve low sidelobes and good cross-polarization performance. The flare angle, length, and aperture size determine the gain, beamwidth, and aperture efficiency. The horn’s impedance is designed to match the feed line to free space to minimize reflections.

Located at the focus of a dish, the feedhorn transmits or receives signals and couples to the parabolic reflector to form a directional beam. It may drive a low-noise amplifier or receiver directly or through a waveguide-to-coax transition, and may support dual polarization via an orthomode transducer or separate feeds.

Applications include satellite communications, radio astronomy, radar, and wireless backhaul. In space and ground-based systems, feedhorns are designed for specific frequency bands and polarizations, such as X, Ku, or Ka bands in satellite links. Corrugated and dual-polarization feeds are common where low sidelobes and good polarization isolation are required.

Manufacture typically uses aluminum or copper, with precise machining or electroforming for corrugations; tolerances are important to preserve phase center location and beam quality.