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| [[Image:L-over2-rad-pat-per.jpg|thumb|The [[radiation pattern]] of a simple omnidirectional antenna, a vertical half-wave [[dipole antenna]]. In this graph the antenna is at the center of the "donut," or [[torus]]. Radial distance from the center represents the power radiated in that direction. The power radiated is maximum in horizontal directions, dropping to zero directly above and below the antenna.]]
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| In [[radio communication]], an '''omnidirectional antenna''' is a class of [[antenna (electronics)|antenna]] which radiates [[radio wave]] power uniformly in all directions in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. This [[radiation pattern]] is often described as "doughnut shaped". Note that this is different from an [[isotropic radiator|isotropic antenna]], which radiates equal power in ''all'' directions and has a "spherical" radiation pattern. Omnidirectional antennas oriented vertically are widely used for nondirectional antennas on the surface of the Earth because they radiate equally in all horizontal directions, while the power radiated drops off with elevation angle so little radio energy is aimed into the sky or down toward the earth and wasted. Omnidirectional antennas are widely used for [[radio broadcasting]] antennas, and in mobile devices that use radio such as [[cell phone]]s, [[FM radio]]s, [[walkie-talkie]]s, [[Wireless network|wireless computer networks]], [[cordless phone]]s, [[GPS]] as well as for base stations that communicate with mobile radios, such as police and taxi dispatchers and aircraft communications.
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| ==Types==
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| [[Image:Vpol dual band blade antenna blade L1 3D.jpg|thumb|Radiation pattern of a 3λ/2 [[monopole antenna]]. Although the radiation of an omnidirectional antenna is symmetrical in azmuthal directions, it may vary in a complicated way with elevation angle, having ''lobes'' and ''nulls'' at different angles. ]]
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| Common types of low-gain omnidirectional antennas are the [[whip antenna]], [[Rubber Ducky antenna|"Rubber Duck" or "Rubber Ducky"]], [[Monopole antenna|ground plane antenna]], vertically oriented [[dipole antenna]], [[discone antenna]], [[mast radiator]], horizontal [[loop antenna]] (sometimes known colloquially as a 'circular aerial' because of the shape), and the [[halo antenna]].
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| Higher-gain omnidirectional antennas can also be built. "Higher gain" in this case means that the antenna radiates less energy at higher and lower elevation angles and more in the horizontal directions. High-gain omnidirectional antennas are generally realized using collinear dipole arrays. These arrays consist of half-wavelength dipoles with a phase shifting method between each element that ensures the current in each dipole is in phase.<ref>{{cite book |editor=Johnson, R, Jasik, H |title=Antenna Engineering Handbook |publisher=McGraw Hill |location= |year=1984 |isbn= |pages=27–14 }}</ref> The [[Coaxial Colinear]] or COCO antenna uses transposed coaxial sections to produce in-phase half-wavelength radiators. A [[Franklin Array]] uses short U-shaped half-wavelength sections whose radiation cancels in the far-field to bring each half-wavelength dipole section into equal phase.
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| Types of higher gain omnidirectional antennas are the coaxial collinear (COCO) antenna<ref>{{cite journal |doi=10.1109/8.18724 |author=Judasz, T., Balsley, B. |title=Improved Theoretical and Experimental Models for the Coaxial Colinear Antenna |journal=IEEE Transactions on Antennas and Propagation |volume=37 |issue=3 |pages=289–296 |date=March 1989 }}</ref> and Omnidirectional [[Microstrip antenna|Microstrip Antenna]] (OMA).<ref>{{cite journal |doi=10.1002/mop.21187 |author=Bancroft R |title=Design Parameters of an Omnidirectional Planar Microstrip Antenna |journal=Microwave and Optical Technology Letters |volume=47 |issue=5 |pages=414–8 |date=December 5, 2005 }}</ref>
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| Some planar antennas (constructed from printed circuit board) are omnidirectional antennas.<ref>{{cite web |author=Yanaga; Kurashima; Arita; Kobayashi |title=A Planar UWB Monopole Antenna Formed on a Printed Circuit Board |year=2003? |work= |publisher= |url=http://www.fujitsu.com/downloads/MICRO/fcai/input/uwb_monopole_antenna.pdf |format=PDF}}</ref>
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| ==Analysis==
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| [[Image:Schwarzbeck RE 1790.jpg|right|thumb|240px|Vertical polarized VHF- UHF [[biconical antenna]] 170 – 1100 MHz with omni directional H-plane pattern]]
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| Omnidirectional radiation patterns are produced by the simplest practical antennas, [[monopole antenna|monopole]] and [[dipole antenna]]s, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna [[directivity]] (D) which is expressed mathematically as: <math>G = eD</math>. A useful relationship between omnidirectional radiation pattern [[directivity]] (D) in [[decibels]] and half-power [[beamwidth]] (HPBW) based on the assumption
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| of a <math>\sin{b\theta} / {b\theta}</math> pattern shape is:<ref>{{cite journal |author=McDonald, Noel |title=Omnidirectional Pattern Directivity in the Presence of Minor Lobes: Revisited |journal=IEEE Transactions on Antennas and Propagation |volume=41 |issue=2 |pages=63–8 |date=April 1999 |doi= |url=}}</ref>
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| <math> D = 10\log_{10} {\left ({101.5\over {HPBW - 0.00272(HPBW)^2}}\right )} \;\; dB.</math>
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| ==See also==
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| * [[Choke ring antenna]]
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| * [[Directional antenna]]
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| ==References==
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| {{Reflist}}
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| [[Category:Radio frequency antenna types]]
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His name is Alfonso Szabo yet it's not the most masucline name out there. What her family and her love is to handle archery and she'll be starting something else along in addition to. Years ago she moved to Kansas. Invoicing is what she does for but she plans on changing this. I'm not able at webdesign a person might need to check my website: http://vazquezn1.wordpress.com/2014/06/17/la-fibra-de-vidrio-un-elemento-preciado-con-considerable-potencial-en-el-reciclaje/
My webpage :: epoxi resina