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driven and parasitic elements wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 driven elements 2 parasitic elements 3 references 4 further reading toggle the table of contents driven and parasitic elements 1 language magyar edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia redirected from passive radiator radio aerial composed of directly connected and passive elements passive radiator redirects here for the speaker enclosure see passive radiator speaker parasitic element redirects here for unwanted electrical circuit components see parasitic impedance yagi antenna with one driven element a called a folded dipole and 5 parasitic elements one reflector b and 4 directors c the feed line leading to the receiver is not shown it attaches to the driven element at d the antenna radiates radio waves in a beam toward the right part of a series on antennas common types dipole fractal loop monopole satellite dish television whip components balun block upconverter coaxial cable counterpoise ground system feed feed line low noise block downconverter passive radiator receiver rotator stub transmitter tuner twin lead systems antenna farm amateur radio cellular network hotspot municipal wireless network radio radio masts and towers wi fi wireless safety and regulation wireless device radiation and health wireless electronic devices and health international telecommunication union radio regulations world radiocommunication conference radiation sources regions boresight focal cloud ground plane main lobe near and far field side lobe vertical plane characteristics array gain directivity efficiency electrical length equivalent radius factor friis transmission equation gain height radiation pattern radiation resistance radio propagation radio spectrum signal to noise ratio spurious emission techniques beam steering beam tilt beamforming small cell bell laboratories layered space time blast massive multiple input multiple output mimo reconfiguration spread spectrum wideband space division multiple access wsdma v t e in an antenna array made of multiple conductive elements typically metal rods a driven element or active element also called driven radiator or active radiator is electrically connected to the receiver or transmitter while a parasitic element or passive radiator is not driven elements edit this section does not cite any sources please help improve this section by adding citations to reliable sources unsourced material may be challenged and removed april 2016 learn how and when to remove this message active element redirects here for the devices used in electronic circuits see active component in a multielement antenna array such as a yagi uda antenna the driven element or active element is an antenna element that is directly excited by the feed system in a transmitting antenna or from which the received signal is taken in a receiving antenna in a transmitting antenna it is driven or excited by the radio frequency current from the transmitter and is the source of the radio waves in a receiving antenna it couples energy from the incoming electromagnetic wave into an electrical signal in the antenna circuit which are applied to the receiver multielement antennas like the yagi typically consist of a driven element connected to the receiver or transmitter through a feed line and a number of other elements which are not driven called parasitic elements the driven element is often a dipole the parasitic elements couple electromagnetically with the driven element and re radiate the induced currents modifying the radiation pattern and impedance of the antenna and serve to modify the radiation pattern of the antenna directing the radio waves in one direction increasing the gain of the antenna an antenna may have more than one driven element although the most common multielement antenna the yagi usually has only one for example transmitting antennas for am radio stations often consist of several mast radiators each of which functions as a half wave monopole driven element to create a particular radiation pattern under the appropriate array theory assumptions two elements spaced λ 4 and carrying equal amplitude currents with a 90 relative phase can produce a cardioid type array factor a log periodic antenna lpda consists of many dipole elements of decreasing length all of which are driven however because they are different lengths only one of the many dipoles is resonant at a given frequency so only one is driven at a time the position of the active region depends on the frequency of the signal with different groups of elements contributing most strongly at different frequencies phased arrays may have hundreds of driven elements household multiband television antennas often combine a yagi type uhf section with a log periodic or similar broadband vhf section the vhf and uhf sections are combined through an appropriate feed or matching network typically providing a 75 ω output for the coaxial downlead when a driven element is referred to in an antenna array it is often assumed that other elements are not driven i e passive radiator and that the array is tightly coupled spacing far below a wavelength parasitic elements edit parasitic element redirects here for the unwanted circuit elements see parasitic element electrical networks this article needs more citations please help improve this article by adding citations to reliable sources unsourced material may be challenged and removed find sources driven and parasitic elements news newspapers books scholar jstor december 2009 learn how and when to remove this message in a radio antenna a parasitic element or passive radiator is a conductive element typically a metal rod which is not electrically connected to anything else 1 multielement antennas such as the yagi uda antenna typically consist of a driven element which is connected to the radio receiver or transmitter through a feed line and parasitic elements which are not the purpose of the parasitic elements is to modify the radiation pattern of the radio waves emitted by the driven element directing them in a beam in one direction increasing the antenna s directivity gain a parasitic element does this by acting as a passive resonator something like a guitar s sound box absorbing the radio waves from the nearby driven element and re radiating them again with a different phase the waves from the different antenna elements interfere strengthening the antenna s radiation in the desired direction and cancelling out the waves in undesired directions the parasitic elements in a yagi antenna are mounted parallel to the driven element with all the elements usually in a line perpendicular to the direction of radiation of the antenna what effect a parasitic element has on the radiation pattern depends both on its separation from the next element and on its length the driven element of the antenna is usually a half wave dipole its length half a wavelength of the radio waves used the parasitic elements are of two types a reflector is slightly longer around 5 than a half wavelength it serves to reflect the radio waves in the opposite direction a director is slightly shorter than a half wavelength it serves to increase the radiation in a given direction a yagi antenna may have a reflector on one side of the driven element and one or more directors on the other side if all the elements are in a plane usually only one reflector is used because additional ones give little improvement in gain but sometimes additional reflectors are mounted above and below the plane of the antenna on a vertical bracket at the end yagi antenna for uhf tv reception with 22 parasitic elements 4 reflectors attached to the vertical bracket at left and 18 directors attached to the horizontal beam at right the driven element is attached to the black box next to the reflectors the antenna is most sensitive to radio waves coming from the right parallel to the antenna s axis all the elements are usually mounted on a metal beam or bracket along the antenna s central axis although sometimes the parasitic elements are insulated from the supporting beam often they are clamped or welded directly to it electrically connected to it this doesn t affect their functioning because the rf voltage distribution along the element is maximum at the ends and goes to zero has a node at the midpoint where the grounded beam is attached the addition of parasitic elements gives a diminishing improvement in the antenna s gain 2 adding a reflector to a dipole to make a 2 element yagi increases the gain by about 5 db over the dipole adding a director to this to give a 3 element yagi gives a gain of about 7 db over a dipole as a rule of thumb each additional parasitic element beyond this adds about 1 db of gain 2 in an example of a parasitic element that is not rod shaped a parasitic microstrip patch antenna is sometimes mounted above another driven patch antenna this antenna combination resonates at a slightly lower frequency than the original element however the main effect is to greatly increase the impedance bandwidth of the antenna in some cases the bandwidth can be increased by a factor of 10 comparison of a yagi with parasitic elements to a log periodic with all active elements not all types of thin conductor multielement antennas have parasitic elements the log periodic antenna is similar in appearance to a yagi but all of its elements are driven elements connected to the transmitter or receiver references edit poole ian 2010 the yagi antenna radio electronics com adrio communications retrieved 2011 03 29 1 2 poole ian 2003 newnes guide to radio and communications technology elsevier pp 102 191 isbn 0 7506 5612 3 via google books further reading edit arrl antenna book 23 ed newington ct american radio relay league 2015 subsection 11 1 isbn 978 1625950444 retrieved from https en wikipedia org w index php title driven_and_parasitic_elements oldid 1371222306 category antennas radio hidden categories articles with short description short description matches wikidata articles needing additional references from april 2016 all articles needing additional references articles needing additional references from december 2009 this page was last edited on 25 august 2026 at 07 27 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is a registered trademark of the wikimedia foundation inc a non profit organization privacy policy about wikipedia disclaimers contact wikipedia legal safety contacts code of conduct developers statistics cookie statement mobile view search search toggle the table of contents driven and parasitic elements 1 language add topic
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