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In antenna theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are set in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.〔 (Definition of Phased Array ). Accessed April 27, 2006.〕 The phase relationships among the antennas may be fixed, as is usual in a tower array, or may be adjustable, as for beam steering. == History == Phased array transmission was originally shown in 1905 by Nobel laureate Karl Ferdinand Braun who demonstrated enhanced transmission of radio waves in one direction.〔http://nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.pdf Braun's Nobel Prize lecture. The phased array section is on pages 239–240.〕〔"Die Strassburger Versuche über gerichtete drahtlose Telegraphie" (The Strassburg experiments on directed wireless telegraphy), ''Elektrotechnische und Polytechnische Rundschau'' (Electrical technology and polytechnic review (weekly )), (1 November 1905). This article is summarized (in German) in: Adolf Prasch, ed., ''Die Fortschritte auf dem Gebiete der Drahtlosen Telegraphie'' (in the field of wireless telegraphy ) (Stuttgart, Germany: Ferdinand Enke, 1906), vol. 4, (pages 184-185 ).〕 During World War II, Nobel laureate Luis Alvarez used phased array transmission in a rapidly steerable radar system for "ground-controlled approach", a system to aid in the landing of aircraft. At the same time, the GEMA in Germany built the PESA Mammut 1.〔http://www.100jahreradar.de/index.html?/gdr_5_deutschefunkmesstechnikim2wk.html Mamut1 first early warning PESA Radar〕 It was later adapted for radio astronomy leading to Nobel Prizes for Physics for Antony Hewish and Martin Ryle after several large phased arrays were developed at the University of Cambridge. This design is also used for radar, and is generalized in interferometric radio antennas. In 2007, DARPA researchers announced a 16 element phased array radar antenna which was also integrated with all the necessary circuits on a single silicon chip and operated at 30–50 GHz.〔(World’s Most Complex Silicon Phased Array Chip Developed at UC San Diego ) in UCSD News (reviewed 02. November 2007)〕 The relative amplitudes of—and constructive and destructive interference effects among—the signals radiated by the individual antennas determine the effective radiation pattern of the array. A phased array may be used to point a fixed radiation pattern, or to scan rapidly in azimuth or elevation. Simultaneous electrical scanning in both azimuth and elevation was first demonstrated in a phased array antenna at Hughes Aircraft Company, California in 1957.〔See Joseph Spradley, "A Volumetric Electrically Scanned Two-Dimensional Microwave Antenna Array," IRE National Convention Record, Part I – Antennas and Propagation; Microwaves, New York: The Institute of Radio Engineers, 1958, 204–212.〕 Phased arrays are used in optical communication as a wavelength-selective splitter. For information about active and passive phased array radars, see also active electronically scanned array. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phased array」の詳細全文を読む スポンサード リンク
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