A feed horn (or feedhorn) is a small

horn antenna A horn antenna or microwave horn is an antenna (radio), antenna that consists of a flaring metal waveguide shaped like a horn (acoustic), horn to direct radio waves in a beam. Horns are widely used as antennas at Ultrahigh frequency, UHF and m ...

used to couple a

waveguide A waveguide is a structure that guides waves by restricting the transmission of energy to one direction. Common types of waveguides include acoustic waveguides which direct sound, optical waveguides which direct light, and radio-frequency w ...

to e.g. a parabolic dish antenna or

offset dish antenna An offset dish antenna or off-axis dish antenna is a type of parabolic antenna. It is so called because the antenna feed is offset to the side of the reflector, in contrast to the common "front-feed" parabolic antenna where the feed antenna is ...

for reception or transmission of

microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

s. A typical application is the use for

satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...

reception with a

satellite dish A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish which receives direct-broadcast satellite televisio ...

. In that case the feed horn can either be a separate part used together with e.g. a "

low-noise block downconverter A low-noise block downconverter (LNB) is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish and converts them to a signal which is sent through a cable to the receiver ...

" (LNB), or more typically today is integrated into a "low-noise block feedhorn" (LNBF).

Principle of operation

The feed horn minimizes the mismatch loss between the antenna and the waveguide. If a simple open-ended waveguide would be used, without the horn, the sudden end of the conductive walls causes an abrupt impedance change at the aperture, between the

wave impedance The wave impedance of an electromagnetic wave is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right angles to the direction of propagation). For a transverse-electric-magnetic ...

in the waveguide and the

impedance of free space In electromagnetism, the impedance of free space, , is a physical constant relating the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through free space. That is, Z_0 = \frac, where is the electric fie ...

(see

for more details). When used with a offset, parabolic or

lens antenna A lens antenna is a directional antenna that uses a shaped piece of microwave-transparent material to bend and focus microwaves by refraction, as an optical lens does for light. Typically it consists of a small feed antenna such as a patch an ...

, the

phase center In antenna design theory, the phase center is the point from which the electromagnetic radiation spreads spherically outward, with the phase of the signal being equal at any point on the sphere. Apparent phase center is used to describe the phas ...

of the horn is placed at the focal point of the reflector. The characteristic of the feed horn is usually selected with the of the horn's

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...

falling on the edge of the reflector (the

beamwidth The beam diameter or beam width of an electromagnetic beam is the diameter along any specified line that is perpendicular to the beam axis and intersects it. Since beams typically do not have sharp edges, the diameter can be defined in many differ ...

of the horn matching the F/D ratio of the dish). When the shape of the antenna deviates from a circular dish, the feedhorn needs to be shaped accordingly to illuminate the antenna properly.

Applications

For satellite TV reception the feedhorn is mounted at the feed arm of the

. The feedhorn then connects via a short waveguide to the "

" (LNB), a small housing containing a part of the reception electronics (also called the "

RF front end In a radio receiver circuit, the RF front end, short for ''radio frequency front end'', is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage. It consists of all the components in the ...

"). This LNB converts the high satellite microwave downlink frequencies to lower frequencies, so the TV signals can be more easily transmitted through

coaxial cable Coaxial cable, or coax (pronounced ), is a type of electrical cable consisting of an inner Electrical conductor, conductor surrounded by a concentric conducting Electromagnetic shielding, shield, with the two separated by a dielectric (Insulat ...

s to receivers located anywhere inside a building. For DTH TV typically the LNB and the feedhorn are integrated into one unit called "low-noise block feedhorn" (LNBF), but separate feedhorns and LNBs are used for more specialized applications. For

satellite uplink A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. ...

(e.g. for transmission of "Direct-To-Home" DTH TV programs,

satellite news gathering Electronic news gathering (ENG) or electronic journalism (EJ) is usage of electronic video and audio technologies by reporters to gather and present news instead of using film cameras. The term was coined during the rise of videotape techno ...

SNG,

satellite internet access Satellite Internet access is Internet access provided through communication satellites; if it can sustain high-speed Internet, high speeds, it is termed satellite broadband. Modern consumer grade satellite Internet service is typically provide ...

VSAT A very-small-aperture terminal (VSAT) is a two-way satellite ground station with a satellite dish, dish antenna that is smaller than 3.8 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Bit rates, in most cases, range from 4 ...

applications) a

block upconverter A block upconverter (BUC) is a component used in the transmission (uplink) of satellite signals. It converts a band of frequencies from a lower frequency to a higher frequency. Modern BUCs convert from the L band to Ku band, C band and Ka ...

(BUC) connects via a waveguide to the feedhorn, in order to transmit via the satellite dish to the

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Rad ...

. Feedhorns are also used in applications like

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

, line-of-sight

microwave transmission Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz (1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signal ...

radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object, celestial objects using radio waves. It started in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observat ...

References

{{DEFAULTSORT:Feed Horn Radio frequency antenna types Satellite broadcasting Antennas (radio) pl:Konwerter satelitarny

Principle of operation

Applications

See also

References