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A directional antenna or beam antenna is an antenna which radiates or receives greater power in specific directions allowing increased performance and reduced interference from unwanted sources. Directional antennas provide increased performance over dipole antennas —or omnidirectional antennas in general—when greater concentration of radiation in a certain direction is desired. A high-gain antenna HGA is a directional antenna with a focused, narrow radiowave beam width, permitting more precise targeting of the radio signals.

Most commonly referred to during space missionsthese antennas are also in use all over Earthmost successfully in High gain dipole antenna, open areas where there are no mountains to disrupt radiowaves.

By contrast, a low-gain High gain dipole antenna LGA is an omnidirectional antenna with a broad radiowave beam width, that allows the signal to propagate reasonably well even in mountainous regions and is thus more reliable regardless of terrain.

Low-gain antennas are often used in spacecraft as a backup to the high-gain antennawhich transmits a much narrower beam and is therefore susceptible to loss of signal.

All practical antennas are at least somewhat directional, although usually only the direction in the plane parallel to the earth is considered, and practical antennas can easily be omnidirectional in one plane. The most common types are the Yagi antennathe log-periodic antennaand the corner reflector antennawhich are frequently combined and High gain dipole antenna sold as residential TV antennas. Cellular repeaters often make use of external directional antennas to give a far greater signal than can be obtained on a standard cell phone.

Satellite Television receivers usually use parabolic antennas. For long and medium wavelength frequenciestower arrays are used in most cases as directional antennas.

When transmitting, a high-gain antenna allows more of the transmitted power to be sent in the direction of the receiver, increasing the received signal strength. When receiving, a high gain antenna captures more of the signal, again increasing signal strength. Due to reciprocitythese two effects are equal—an antenna that makes a transmitted signal times stronger compared to an isotropic radiator will also capture times as much energy as the isotropic antenna when used as a receiving antenna.

As a consequence of their directivity, directional antennas also send less and receive less signal from directions other than the main beam. This property may be used to reduce interference.

There are many ways to make a high-gain antenna; the most common are parabolic antennashelical antennasyagi antennasand phased High gain dipole antenna of smaller antennas of any kind. Horn antennas can also be constructed with high gain, but are less commonly seen. Still other configurations are possible—the Arecibo Observatory uses a combination of a line feed with an enormous spherical reflector as opposed to a more usual parabolic reflectorto achieve High gain dipole antenna high gains at specific frequencies.

Antenna gain is often quoted with respect to a hypothetical antenna that radiates equally in all directions, an isotropic radiator. This gain, when measured in decibelsis called dBi. Conservation of energy dictates that high gain antennas must have narrow beams.

In turn this implies that high-gain antennas must be physically large, since according to the diffraction limit High gain dipole antenna, the narrower the beam desired, the larger the High gain dipole antenna must be measured in wavelengths.

Antenna gain can also be measured in dBd, which is gain in Decibels compared to the maximum intensity direction of a half wave dipole. In the case of Yagi type aerials this more or less equates to the gain one would expect from the aerial under test minus all its directors and reflector.

It is important not to confuse dBi and dBd; the two differ by 2. Gain is also dependent on the number of elements and the tuning of those elements. Antennas can be tuned to be resonant over a High gain dipole antenna spread of frequencies but, all other things being equal, this will mean the gain of the aerial is lower than one tuned for a single frequency or a group of frequencies.

For example, in the case of wideband TV antennas the fall off in gain is particularly large at the bottom of the TV transmitting band. Other factors may also affect gain such as aperture the area the antenna collects signal from, almost entirely related to the size of the antenna but for small antennas can be increased by adding a ferrite rodand efficiency again, affected by size, but also resistivity of the materials used and impedance matching.

These factors are easy to improve without adjusting other features of the antennas or coincidentally improved by the same factors that increase directivity, and so are typically not emphasized. High gain antennas are typically the largest component of deep space probes, and the highest gain radio antennas are physically enormous structures, such as the Arecibo Observatory. However, the optimum scheduling of concurrent transmission is an NP-Hard problem [2]. A Yagi-Uda antenna. From left to right, the elements mounted on the boom are called the reflector, driven element, and director.

A giant phased-array radar in Alaska. Holmdel Horn Antenna in High gain dipole antenna, New Jersey Built to support the Echo satellite communication program, [3] it was later used in experiments that revealed the cosmic background radiation permeating the High gain dipole antenna. Voyager 2 spacecraft. The HGA a parabolic antenna is the large bowl-shaped object. From Wikipedia, the free encyclopedia.

Redirected from High-gain antenna. A multi-element, log-periodic dipole array. This section contains what may be an unencyclopedic or excessive gallery of images. Galleries containing indiscriminate images of the High gain dipole antenna subject are discouraged ; please help improve the section by reducing indiscriminate gallery sections or by moving relevant images beside adjacent text, in accordance with the Manual of Style on use of images.

January Learn how and when to remove this template message. Helical antenna. Amateur radio direction finding Antenna gain Cantenna Cardioid Cassegrain antenna Cassegrain reflector Loop antenna Omnidirectional antenna Parabolic antenna Phased array High gain dipole antenna direction finder Radio propagation modelAntenna subsection.

ETRI Journal. Hogg and L. Hunt July The Bell System Technical Journal : — Archived from the original on Retrieved Antenna types. Isotropic radiator. Categories : Radio frequency antenna types Radio frequency propagation Antennas radio. Hidden categories: CS1 errors: missing periodical CS1 maint: multiple names: authors list. Namespaces Article Talk. Views Read Edit View history. By using this site, you agree to the Terms of Use and Privacy Policy.


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