Wide-band High-gain Yagi Antenna

As a typical end-fire antenna, Yagi antenna has the advantages of simple structure, convenient feeding, good directivity, but its narrow band always restricts the application of Yagi antenna. This dissertation mainly studies the broadband design and reconfigurable design of Yagi antenna.Firstly, this dissertation will make a brief introduction of the basic theory of Yagi antenna and design a low-profile Yagi antenna based on thin-film technology by the traditional design method, and then puts forward the question of how to broaden the bandwidth of Yagi antenna.Then, this dissertation summarizes the methods of broadening the bandwidth of antennas, and designs two new low-profile wideband Yagi antennas, which use open sleeve dipole and stub-loaded resonator as the active oscillator of Yagi antenna respectively. The simulation results of the two antennas are presented. The new broadband Yagi antennas working in UHF band, and can achieve a relative impedance bandwidth of more than 30%. The designed antennas have good directivity within the impedance bandwidth and can reach a maximum radiation gain of 14 d Bi. Dissertation gives the simulation results and analysis of design antennas.Finally, the reconfigurable design of wideband Yagi antennas is studied. The designed Yagi antennas can realize frequency reconfiguration and pattern reconfiguration respectively by using PIN diode and varactor diodes. The designed frequency reconfigurable Yagi antenna can change the working frequency without changing the antenna’s radiation pattern, which can further expand the impedance bandwidth of the antenna up to a octave. The designed pattern reconfigurable Yagi antenna, works in the UHF band with a relative impedance bandwidth of more than 30%, which can switch in the four beams.