Horn antenna

A horn (English horn antenna ) is a construction of an antenna for microwaves and consisting of a more or less approximated to the form of a metal surface Exponentialtrichters which opens generally in a waveguide.

Horn are used as independent emitters or to feed at the focus of parabolic antennas (radar antennas, radio telescopes, radio antennas, shell antennas).

Different models also led to names such as pyramidal horn and tapered horn.

Principle

In principle, the waveguide that directs the transmitter power to the antenna radiate from its open end of the electromagnetic wave in free space. The characteristic impedance of the vacuum has a value other than the waveguide. For this reason, contact at this point to unwanted reflections. Therefore, it extends on the mechanical dimensions of the waveguide at the point of exit of the electromagnetic wave radiation, to achieve a gradual transition. This construction is called because of the horn-like shape horn.

In microwave antennas, the combination of a primary radiator and a secondary reflector is common, often with a horn radiator (feed) is used as a primary radiator in the focal point of a parabolic mirror metal.

Properties

Horn have a pretty good directivity. The larger the geometrical dimensions of the horn antenna, the better the directivity, and hence the gain. A wall of the horn may be shaped as a section of a paraboloid; the feeding waveguide impinges laterally on the horn. This form is particularly high directivity and front to back ratios are achieved. This form was formerly with radio telescopes and a radio antenna used, there were dimensions realized with several meters of width.

In modern installations for satellite communications to power parabolic antennas mostly corrugated horn lamps are used. These allow a smaller overall length and width. The size of horns is frequency dependent - the higher the radiated or receivable frequency, the smaller can horn and horn grooves are built. The dimensions range from about 20 mm to 100 mm diameter for the supply of satellite dishes up to several meters in diameter at paraboloid horn antennas.

Web horn

A special design is the web horn, often called double Steghorn (English double -ridged waveguide horn ). In this case, the horn is in the middle of the upper and lower wide side exponentially outwardly opening metallic bars which bring about a significant increase in the bandwidth of the antenna. A relative bandwidth of at least 6 is typically accomplished such whereby the horn is also suitable for the emission of pulses. A planar version of the web horn represents the Vivaldi antenna