Difference between revisions of "Antenna"
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==Origin== | ==Origin== | ||
Medieval Latin, from Latin, sail yard | Medieval Latin, from Latin, sail yard | ||
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==Definitions== | ==Definitions== | ||
*1:plural ''an·ten·nae'' : one of a pair of slender movable segmented [[sensory]] organs on the head of insects, myriapods, and crustaceans | *1:plural ''an·ten·nae'' : one of a pair of slender movable segmented [[sensory]] organs on the head of insects, myriapods, and crustaceans | ||
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An '''antenna''' (or aerial) is an [[electrical]] device which converts [[electric]] currents into [[radio]] waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio [[frequency]] electric current to the antenna's terminals, and the antenna [[radiates]] the energy from the current as [[electromagnetic]] [[waves]] (radio waves). In reception, an antenna intercepts some of the [[power]] of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified. An antenna can be used for both transmitting and receiving. | An '''antenna''' (or aerial) is an [[electrical]] device which converts [[electric]] currents into [[radio]] waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio [[frequency]] electric current to the antenna's terminals, and the antenna [[radiates]] the energy from the current as [[electromagnetic]] [[waves]] (radio waves). In reception, an antenna intercepts some of the [[power]] of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified. An antenna can be used for both transmitting and receiving. | ||
| − | Antennas are essential components of all equipment that uses [[radio]]. They are used in systems such as [ | + | Antennas are essential components of all equipment that uses [[radio]]. They are used in systems such as [https://en.wikipedia.org/wiki/Radio_broadcasting radio broadcasting], [https://en.wikipedia.org/wiki/Broadcast_television broadcast television], two-way radio, communications receivers, radar, cell phones, and [[satellite]] communications, as well as other devices such as garage door openers, wireless microphones, [https://en.wikipedia.org/wiki/Bluetooth bluetooth] enabled devices, wireless computer networks, baby monitors, and [https://en.wikipedia.org/wiki/RFID_tag RFID tags] on merchandise. |
| − | Typically an antenna consists of an arrangement of metallic [ | + | Typically an antenna consists of an arrangement of metallic [https://en.wikipedia.org/wiki/Conductor_(material) conductors] ("elements"), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of [[electrons]] forced through the antenna by a transmitter will create an oscillating [[magnetic]] field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields [[radiate]] away from the antenna into [[space]] as a moving [[electromagnetic]] field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna. |
| − | Antennas may also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, [ | + | Antennas may also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, [https://en.wikipedia.org/wiki/Parabolic_antenna parabolic reflectors] or horns, which serve to direct the [[radio]] waves into a beam or other desired [[radiation]] [[pattern]]. Antennas can be [[designed]] to transmit or receive radio waves in all [[directions]] equally ([https://en.wikipedia.org/wiki/Omnidirectional_antenna omnidirectional antennas]), or transmit them in a beam in a particular [[direction]], and receive from that one direction only (directional or [https://en.wikipedia.org/wiki/High_gain_antenna high gain antennas]). |
| − | The first antennas were built in 1888 by German physicist [ | + | The first antennas were built in 1888 by German physicist [https://en.wikipedia.org/wiki/Heinrich_Hertz Heinrich Hertz] in his pioneering [[experiments]] to prove the existence of [[electromagnetic]] waves predicted by the [[theory]] of [https://en.wikipedia.org/wiki/James_Clerk_Maxwell James Clerk Maxwell]. Hertz placed dipole antennas at the [[focal point]] of [https://en.wikipedia.org/wiki/Parabolic_reflector parabolic reflectors] for both transmitting and receiving. He published his work in ''[https://en.wikipedia.org/wiki/Annalen_der_Physik_und_Chemie Annalen der Physik und Chemie]'' (vol. 36, 1889). |
[[Category: Physics]] | [[Category: Physics]] | ||
Latest revision as of 23:43, 12 December 2020
Origin
Medieval Latin, from Latin, sail yard
Definitions
- 1:plural an·ten·nae : one of a pair of slender movable segmented sensory organs on the head of insects, myriapods, and crustaceans
- 2: a usually metallic device (as a rod or wire) for radiating or receiving radio waves
- 3: antennae plural : a special sensitivity or receptiveness <his political antennae proved to be shrewder than ever — Erich Segal>
Description
An antenna (or aerial) is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified. An antenna can be used for both transmitting and receiving.
Antennas are essential components of all equipment that uses radio. They are used in systems such as radio broadcasting, broadcast television, two-way radio, communications receivers, radar, cell phones, and satellite communications, as well as other devices such as garage door openers, wireless microphones, bluetooth enabled devices, wireless computer networks, baby monitors, and RFID tags on merchandise.
Typically an antenna consists of an arrangement of metallic conductors ("elements"), electrically connected (often through a transmission line) to the receiver or transmitter. An oscillating current of electrons forced through the antenna by a transmitter will create an oscillating magnetic field around the antenna elements, while the charge of the electrons also creates an oscillating electric field along the elements. These time-varying fields radiate away from the antenna into space as a moving electromagnetic field wave. Conversely, during reception, the oscillating electric and magnetic fields of an incoming radio wave exert force on the electrons in the antenna elements, causing them to move back and forth, creating oscillating currents in the antenna.
Antennas may also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern. Antennas can be designed to transmit or receive radio waves in all directions equally (omnidirectional antennas), or transmit them in a beam in a particular direction, and receive from that one direction only (directional or high gain antennas).
The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie (vol. 36, 1889).
