hornantenner

Horn antennas, also called horn antennas, are a class of microwave antennas that transition a guided wave in a metal waveguide to a radiated field in free space. They consist of a flared conducting section, shaped either as a pyramid (pyramidal horn) or a cone (conical horn), mounted on a waveguide feed. The flare provides an impedance match and gradually converts the TE/TM modes inside the waveguide into a beam that emerges from the horn aperture.

Construction and variants: Horns are typically made from aluminum or copper and are designed with a smooth interior surface to minimize losses. The flare angle and the size of the aperture determine the antenna’s gain, beamwidth, and bandwidth. Common variants include pyramidal horns, conical horns, and double-ridged horns for broader frequency coverage. They are often used as standalone radiators or as feed horns for parabolic reflectors or antenna test setups.

Operation and performance: The horn’s aperture behaves as an optical-like aperture antenna, producing a directive radiation pattern with relatively low sidelobes and stable beamwidth. The directivity increases with the aperture area, while bandwidth depends on the horn geometry and the feed. Horn antennas are valued for their straightforward construction, good impedance matching, and predictable performance, though they can be physically bulky at lower microwave frequencies.

Applications: They are widely used in radar, radio astronomy, satellite and terrestrial microwave communications, and as calibrated sources and receivers in measurement systems. In many systems, a horn antenna serves as the feed for a reflector or as a reference antenna in testing and calibration.

History: Horn antennas were developed in the early microwave era and became a standard tool in radar and communications research due to their simplicity and reliable performance.