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| Yagi–Uda antenna | |
|---|---|
| Name | Yagi–Uda antenna |
| Caption | Typical Yagi–Uda antenna for television reception |
| Frequency | VHF, UHF |
| Inventor | Hidetsugu Yagi; Shintaro Uda |
| Introduction year | 1926 |
| Type | directional antenna |
| Polarization | linear |
| Gain | variable |
| Beamwidth | variable |
Yagi–Uda antenna is a directional antenna widely used for radio, television, and radar reception. Invented in the 1920s, it combines a driven element with parasitic elements to produce significant forward gain and a narrow radiation pattern. The design has influenced communications systems, broadcasting networks, and amateur radio installations worldwide.
The Yagi–Uda concept originated from research at Tohoku Imperial University by Hidetsugu Yagi and Shintaro Uda in 1926, motivated by contemporaneous developments at institutions such as Bell Labs and Marconi Company. Early demonstrations attracted attention from broadcasters like NHK and engineers at Radio Corporation of America and British Broadcasting Corporation who adapted the antenna for television and shortwave services. During the interwar and post‑World War II periods, adoption spread through collaborations involving Sony, Philips, and RCA Victor, shaping standards later overseen by bodies such as the International Telecommunication Union and influencing radar projects at facilities like MIT Radiation Laboratory and Harvard University.
A typical assembly includes a driven element, reflectors, and one or more directors mounted on a boom. The driven element often uses dimensions related to the free‑space wavelength popularized by research from Heinrich Hertz and designs used at Bell Telephone Laboratories. Reflectors and directors are parasitic and shaped following principles studied by engineers at General Electric and Siemens. The boom, insulators, feedline connectors, and matching networks reflect practices standardized by IEEE committees and manufacturers such as Comcast hardware suppliers and construction firms influenced by Edison General Electric Company techniques.
Operation relies on resonant coupling, mutual impedance, and constructive interference, concepts formalized in work by Oliver Heaviside and extended in matrix methods from John von Neumann and Harold Hotelling. The driven element is usually a half‑wave dipole fed by a transmission line; coupling to directors and reflectors shifts current distributions in ways analyzed in studies at Stanford University and California Institute of Technology. Pattern formation and impedance behavior are predicted by methods used in computational electromagnetics originating at Los Alamos National Laboratory and by numerical techniques from Nikola Tesla‑era experiments.
Performance metrics include forward gain, front‑to‑back ratio, bandwidth, and impedance. Gain improvements were quantified in comparative measurements by researchers at National Institute of Standards and Technology and in field tests by broadcasters such as BBC and NPR. Front‑to‑back ratios and sidelobe levels guided deployments at installations like the Palomar Observatory and communication infrastructure overseen by AT&T and Verizon. Bandwidth limitations prompted innovations linked to work at Bell Labs and publications in journals from IEEE Antennas and Propagation Society.
The antenna is employed for terrestrial television broadcasting installations used by networks such as NBC, CBS, and ITV, as well as amateur radio operations coordinated by organizations like American Radio Relay League and Radio Amateurs of Canada. It features in point‑to‑point microwave links by carriers like Vodafone and T-Mobile, in early radar arrays developed at MIT Lincoln Laboratory, and in remote sensing payloads analogous to technologies from NASA and European Space Agency. Educational laboratories at institutions including Massachusetts Institute of Technology and University of Cambridge use Yagi–Uda models to teach antenna theory.
Constructing a Yagi–Uda antenna involves selecting element lengths, spacing, and feed matching, often guided by formulas from classic texts published by Harvard University Press and engineering handbooks used by Siemens and Thomson. Materials range from aluminum tubing used by manufacturers like Rohm and Haas to insulated boom designs influenced by practices at DuPont. Tuning employs techniques such as gamma matches, baluns, and stubs, with iterative measurement practices mirrored in test procedures at National Instruments and calibration routines from NIST.
Variants include log‑periodic arrays developed by Donald B. Isbell, the bi‑quad influenced by Guglielmo Marconi‑era patents, and phased arrays employed by systems at Raytheon and Lockheed Martin. Related directional designs like curtain arrays used by broadcasters such as BBC World Service and rotatable arrays used by observatories including Arecibo Observatory illustrate the evolution of array concepts traced through collaborations involving Bell Labs and MIT Lincoln Laboratory. Modern adaptive and electronically steered adaptations draw on research from DARPA and university centers such as Caltech and Imperial College London.
Category:Radio antennas Category:Telecommunications equipment