Yagi-Uda antenna

Article By:

Izadian, Jamal S. AntennaEM Communication, LLC, San Jose, California.

Last reviewed:June 2020

DOI:https://doi.org/10.1036/1097-8542.752600

An antenna in which the gain of a single dipole element is enhanced by placing a reflector element behind the dipole (the driver) and one or more director elements in front of it (see illustration). Invented in 1926 by H. Yagi, and S. Uda in Japan, the Yagi-Uda antenna is a long-time favorite of amateur radio enthusiasts. The gain is slightly increased by the reflector and further enhanced by the first director element. Additional director elements further increase the gain and improve the front-to-back ratio, up to a point of diminishing returns. This type of antenna has traditionally been used for local television reception. Its variants have found applications in the more modern communication systems at higher frequencies and smaller sizes, and have even been adapted to printed-circuit techniques in some applications. The same electromagnetic induction principle used in such linear elements can be applied to loop and disk elements as well with similar results. See also: Directivity; Electromagnetic induction; Gain; Printed circuit board

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