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How Does the Horn Antenna Work?

The horn antenna is applied to the transmission and reception of microwave signals. It stems from the characteristically unstable appearance. The horn antenna must have a certain minimum size relative to the wavelength of the incoming or outgoing electromagnetic field. If the horn is too small or the wavelength is too large, and the frequency is too low, the antenna will not work effectively. Horn antennas are commonly used as active elements in dish antennas.


Ⅰ. Working principles of horn antenna


The effect of a horn antenna on electromagnetic waves is similar to that of an acoustic horn on sound waves in musical instruments such as trumpets. When a radio wave propagating through the waveguide hits the opening, this impedance step reflects a crucial part of the wave power to the source, so not all energy is radiated. This may be the same as the reflection at an open cable between an optical medium with a low refractive index and a high refractive index such as a glass surface.


When the waveguide is properly excited at one end and opened at the other end, a small amount of energy will be radiated. The reason is that the end of the waveguide does not match the space. If the waveguide port is opened, the mismatch problems will be resolved. This opening of the waveguide causes electromagnetic buzzing.


When the waveguide is terminated by the horn, the sudden discontinuity is replaced by a gradual transition, so the impedance matching is correct. Therefore, all quantities will propagate forward and be radiated. The shape of the radiation field depends on the opening angle of the horn. The cone-shaped horn and the cone-shaped horn emit a pencil-shaped beam, which has obvious directivity on both the vertical and horizontal planes. The fan-shaped beam results in a fan-shaped horn. The double cone horn produces a pom cake-shaped beam in the vertical direction but is uniform on the horizontal plane.


Ⅱ. What are the applications of the horn antenna?


They are usually used for higher antenna formations, such as parabolic antennas, as directional antennas for radar guns, automatic door openers, microwave radiometers, and other equipment. Horn antennas are used for common elements of phased arrays, satellite and microwave communications, for calibration, and other high-gain antennas for electromagnetic interference measurement.


The horn antenna has a high degree of directivity. However, its power radiates out in the shape of a spherical wavefront. Cone wave horns produce pencil beams, and pyramid horns are another more common directional antenna. However, it is not as instructive as the yagi or arrow antenna. Theoretically, the loss of a cone-shaped wave horn is small. So for any horn antenna, the directivity is almost equal to its gain.

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