In the 1926, Dr. Shintaro Uda and Dr. Hidetsugu Yagi of the Tohoku Imperial University invented a directional antenna system consisting of an array of coupled parallel dipoles.
The geometry of the Yagi-Uda array:
The second dipole in the Yagi-Uda array is the only driven element with applied input/output source feed, all the others interact by mutual coupling since receive and reradiate electromagnetic energy; they act as parasitic elements by induced current. It is assumed that an antenna is a passive reciprocal device, then may used either for transmission or for reception of the electromagnetic energy: this well applies to Yagi-Uda also.
The simplest or minimal Yagi-Uda antenna has at least two parasitic elements behind the Driven Element (DE); the antenna with only one parasitic element as Reflector element (Ref) is generally called Yagi antenna. This happens when the electrical length of the parasitic element is greater than the driven element.
If the electrical length of the parasitic element is shorter than the driven element, the radiation pattern reversed and the parasitic element became a Director (D) always in the two-elements of the Yagi antenna.
FAQ's: what does the antenna difference between Yagi-Uda and Yagi? A television set antenna, FM and amateurs radio beam, a lot of WiFi and satellite antennas are not the Yagi?
[ Yagi-Uda basics ]
Copyright © 2008 Yagi-Uda.com, All Rights Reserved.