Basic of Yagi Antenna / Yagi-Uda Aerial : Working and Applications

The Yagi antenna or aerial sometimes called the Yagi-Uda antenna is widely used for broadcast, domestic and commercial radio communications applications where gain and directivity are required from an RF antenna design.

• The yagi uda antenna was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Japan, with a lesser role played by his colleague Hidetsugu Yagi.
• It is a directional antenna consisting of two or more parallel resonant antenna elements in an end-fire array these elements are most often metal rods acting as half-wave dipoles.
• It consists of a single driven element connected to a radio transmitter or receiver through a transmission line.

Working of Yagi Antenna

• In the yagi uda antenna, there are 3 major elements are used that are generally a half-wave folded dipole, a reflector, and directors.
• The yagi uda antenna structure contains one driven element and a reflector while directors can be more than one.
• The yagi uda antenna arrangement is said to be an array of active and parasitic elements.
• The metallic rod acts as the active element as external feeding is provided to it using transmission lines in the dipole.
• The parasitic elements of the structure are the reflector and director.
• The parasitic elements are also metallic rods placed parallel in the line of sight orientation w.r.t the driven element.
• Although, when the dipole is excited using a transmission line then the current flows through the driven element and induces voltages in the parasitic elements.
• The elements are mounted on a center rod, that acts as horizontal support.
• The figure below represents the structure of the Yagi-Uda antenna.

Radiation Pattern of Yagi-Uda Antenna

• The given below diagram shows the radiation pattern of the Yagi-Uda antenna.

Advantages of Yagi Antenna

• High gain is achieved.
• The high directivity is achieved.
• Ease of handling and maintenance.
• Less amount of power is wasted.
• Broader coverage of frequencies.

Disadvantages of Yagi Antenna

• Prone to noise.
• Prone to atmospheric effects.

Applications of Yagi Antenna

• Mostly used for TV reception.
• Used where a single-frequency application is needed.