How it began
Beginning in 1924, in the laboratories of Tohoku Imperial University in Sendai, Professor Hidetsugu Yagi and his assistant Shintaro Uda designed and built a sensitive and highly directional antenna using closely coupled parasitic elements. In 1925 Uda presented the first report of measurement results, showing that a narrow beam could easily be formed by accurately arranging the parasitic elements.
Before it existed
The School of Engineering at Tohoku Imperial University was established in 1919. At the time, popular research topics in electrical engineering were high-power fields such as generators and transformers. Yagi, a founding professor of the Department of Electrical Engineering, instead advocated research in telecommunications, focusing on areas such as vacuum tubes and antennas. The antenna was invented under these circumstances.
How it works
The antenna places parasitic elements, which are not themselves connected to the transmitter or receiver, close to the driven element so that they are coupled to it. When the parasitic elements are accurately arranged, the antenna forms a narrow beam and becomes both sensitive and highly directional.
Where it stands today
In 1995 the IEEE dedicated a Milestone to Tohoku University honoring the invention. It was the first Milestone dedicated in IEEE Region 10, which covers Asia and the Pacific. The plaque is mounted on the university's Katahira Campus in Sendai, where a prototype of the original antenna is also on display.
