A Yagi-Uda Antenna, commonly known simply as a Yagi antenna or Yagi, is a directional antenna system[1] consisting of an array of a dipole and additional closely coupled parasitic elements (usually a reflector and one or more directors). A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive A dipole antenna, developed by Heinrich Rudolph Hertz around 1886, is an antenna with a center- fed Driven element for transmitting A passive radiator or parasitic element is a Radio antenna element which does not have any Wired Input. The dipole in the array is driven, and another element, 5% longer, operates as a reflector. An antenna reflector is a device that reflects Electromagnetic waves It is often a part of an antenna assembly Other shorter parasitic elements are typically added in front of the dipole as directors. This arrangement gives the antenna directionality that a single dipole lacks. A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive Yagis are directional along the axis perpendicular to the dipole in the plane of the elements, from the reflector through the driven element and out via the director(s). If one holds out one's arms to form a dipole and has the reflector behind oneself, one would receive signals with maximum gain from in front of oneself. In Electronics, gain is a measure of the ability of a circuit (often an Amplifier) to increase the power or Amplitude of a
Directional antennas, such as the Yagi-Uda, are also commonly referred to as beam antennas[2] or high-gain antennas (particularly for transmitting). A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive The high-gain antenna (HGA is an antenna with a focused narrow radiowave beam width
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Description
Yagi-Uda antennas include one or more director elements, which, by virtue of their being arranged at approximately a one-eighth-wavelength mutual spacing and being progressively slightly shorter than a half wavelength, direct signals of increasingly higher frequencies onto the active dipole. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency.
- See also log-periodic antenna. In Telecommunication, a log-periodic antenna ( LP, also known as a log-periodic array) is a Broadband, multielement
Thus, the complete antenna achieves a distinct response bandwidth determined by the length, diameter, and spacing of all the individual elements; but its overall gain is proportional to its length, rather than simply the number of elements.
All of the elements usually lie in the same plane, typically supported on a single boom or crossbar. The parasitic elements do not need to be coplanar, but can be distributed on both sides of the plane of symmetry. In Geometry, a set of points in space is coplanar if the points all lie in the same geometric plane. Reflection symmetry, line symmetry, mirror symmetry, mirror-image symmetry, or bilateral symmetry is Symmetry with respect
The antenna gain is a function of the number of dipole elements and can be approximated (for the main lobe) as
- GT = 1. 66 * N
Where N is the number of elements (dipoles) in the Yagi-Uda antenna.
Developed Yagi-Uda antennas (including the one pictured) are designed to operate on multiple bands; the resulting design is made more complicated by the presence of a resonant parallel coil and capacitor combination (called a "trap" or LC) in the elements. A coil is a series of loops A coiled coil is a structure where the coil itself is in turn also looping A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors An LC circuit is a variety of resonant circuit or tuned circuit and consists of an Inductor, represented by the letter L and a Capacitor, represented
Traps are used in pairs on a multiband antenna. The trap serves to isolate the outer portion of the element from the inner portion for the trap design frequency.
In practice, the higher frequency traps are located closest to the boom of the antenna. Typically, a triband beam will have 2 pairs of traps per element. For example, a typical triband Yagi-Uda beam covering the 10, 15 and 20 meter bands would have traps for the 10 and 15 meter bands.
The introduction of traps is not without cost—due to their nature, they reduce the overall bandwidth of the antenna and overall efficiency of the array on any given frequency, and radically affect its response in the desired direction.
Coverage example
Shown below is the coverage that could be provided by a 3- or 4-element Yagi-Uda array on the 41-meter shortwave radio broadcasting band. The transmitter driving the array has a power output of 20 kilowatts. The array's main lobe bearing is indicated by the red line from the proposed transmitter location in British Columbia, Canada. This predicted coverage was calculated by the VOACAP program.
History
The Yagi-Uda antenna was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Sendai, Japan, with the collaboration of Hidetsugu Yagi, also of Tohoku Imperial University. Year 1926 ( MCMXXVI) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar. Japanese inventor Professor at Tohoku University, where he invented the Yagi-Uda antenna in 1926 abbreviated to, located in the city of Sendai, Miyagi Prefecture in the Tōhoku Region, Japan, is one of Japan's most prestigious national universities is the capital city of Miyagi Prefecture, Japan, and the largest city in the Tōhoku (northeast region For a topic outline on this subject see List of basic Japan topics. Hidetsugu Yagi (八木 秀次 Yagi Hidetsugu, January 28, 1886 - January 19, 1976) was a Japanese Electrical engineer Yagi published the first English-language reference on the antenna in a 1928 survey article on short wave research in Japan and it came to be associated with his name. Year 1928 ( MCMXXVIII) was a Leap year starting on Sunday (link will display full calendar of the Gregorian calendar. However, Yagi always acknowledged Uda's principal contribution to the design, and the proper name for the antenna is, as above, the Yagi-Uda antenna (or array).
The Yagi was first widely used during World War II for airborne radar sets, because of its simplicity and directionality. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships The Japanese military authorities first became aware of this technology after the Battle of Singapore when they captured the notes of a British radar technician that mentioned "yagi antenna". The Battle of Singapore was fought in the South-East Asian theatre of World War II when the Empire of Japan invaded the Allied stronghold Japanese intelligence officers did not even recognise that Yagi was a Japanese name in this context. When "questioned" the technician said it was an antenna named after a Japanese professor. (This story is analogous to the story of American intelligence officers interrogating German rocket scientists and finding out that Robert Goddard was the real pioneer of rocket technology even though he was not well known in the US at that time. Robert Hutchings Goddard, PhD ( October 5, 1882 &ndash August 10 1945 U )
Despite its being invented in Japan, many Japanese radar engineers were unaware of the design until very late in the war, due to internal fighting between the Army and Navy. A horizontally polarized array can be seen under the left leading edge of Grumman F4F, F6F, TBF Avenger carrier based Navy aircraft. In Astronomy, Geography, Geometry and related sciences and contexts a plane is said to be horizontal at a given point if it is locally WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Vertically polarized arrays can be seen on the cheeks of the P-61 and on the nose cones of many WWII aircraft, notably some versions of the German Junkers Ju 88 R1 fighter-bomber, and the British Bristol Beaufighter night-fighter, and Short Sunderland flying-boat. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The term nose cone is used to refer to the forwardmost section of a Rocket, guided Missile or Aircraft. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The Bristol Beaufighter is also the name of a Car produced by Bristol Cars in the 1980s WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Indeed, the latter had so many antenna elements arranged on its back it was nicknamed the "Flying Porcupine" by German airmen.
Yagi-Uda antennas are widely used by amateur radio operators worldwide for communication on frequencies from shortwave, through VHF/UHF, and into microwave bands. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications Hams often homebrew this type of antenna, and have provided many technical papers and software to the engineering community. See also Amateur radio An amateur radio operator is an individual who typically uses equipment at an Amateur radio station to engage in two-way
Wireless energy transfer
Hidetsugu Yagi attempted wireless energy transfer in February of 1926 with this antenna. Wireless energy transfer or wireless power transmission is the process that takes place in any system where Electrical energy is transmitted from a power Yagi and Uda published their first report on the wave projector directional antenna. Yagi managed to demonstrate a proof of concept, but the engineering problems proved to be more onerous than conventional systems.
See also
External articles and further reading
- H . An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into Cardioid is Closed curve with one Cusp. Definition In Geometry, the cardioid is an Epicycloid with one Cusp. In Physics, in the area of Electrodynamics, the Larmor formula is used to calculate the total power radiated by a nonrelativistic point charge as it accelerates A radio direction finder ( RDF) is a device for finding the direction to a Radio source Direction finding (DF refers to the establishment of the direction from which a received signal was transmitted Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the Yagi, Beam transmission of ultra-shortwaves , Proceedings of the IRE, vol. 16, pp. 715-740, June 1928. The URL is to a 1997 IEEE reprint of the classic article. See also Beam Transmission Of Ultra Short Waves: An Introduction To The Classic Paper By H. Yagi by D. M. Pozar, in Proceedings of the IEEE, Volume 85, Issue 11, Nov. 1997 Page(s):1857 - 1863.
- "Scanning the Past: A History of Electrical Engineering from the Past". Proceedings of the IEEE Vol. 81, No. 6, 1993.
- Shozo Usami and Gentei Sato, "Directive Short Wave Antenna, 1924". IEEE Milestones, IEEE History Center, IEEE, 2005.
- D. Jefferies, "Yagi-Uda antennas". 2004.
- Yagi-Uda Antenna. Simple information on basic design, project and measure of Yagi-Uda antenna. 2008
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