Then the basic antenna, driven element with both Reflector and Director is called three elements Yagi-Uda, with increased directivity or beam Gain.
The reflector and directors in the Yagi-Uda antenna are so coupled into parasitic mode; they mutually alter the radiation parameters of the driven element and for each element of the array. Then the physical discovery consist in the increased gain by narrowing the beam width of the dipole alone in a very genially cheap manner, by the means of simple metallic rod or tube conductors, then focus the electromagnetic energy into the desired directions. Thanks a lot to Dr. Shintaro Uda and Dr. Hidetsugu Yagi for the great discovery/invention.
More than one parasitic element should be axially added in the front of the driven element and each one is called director. As the reflector, the directors (D1…Dn) has not wired directly to the feed point. As the number of director grow, it increase the directivity as the beam gain of the Yagi-Uda system array.
In modern Yagi-Uda design, the parasitic elements should be applied to increase the impedance bandwidth also, much more than a single dipole alone, this is in advance to directional capability of the system to control pattern and impedance with any possible desired combination.
Yagi-Uda antennas are widely used in civilian, simple or professionals, military applications also. Yagi-Uda design is used by lot of amateur radio enthusiast all over the world in advance for any kind of wireless radio communication, television etc.
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