Research On Pattern Reconfigurable Quasi-yagi Antenna

With the rapid development of wireless communication technologies, the properties of the antenna are required to adapt to communication environments. The reconfigurable antenna is a good candidate for modern communication system. Radiation pattern reconfigurable antenna that is one of most important parts in the domain of reconfigurable antennas nowadays can be used to avoid noise environments, improve security and save energy by directing signals only toward intended direction. The printed quasi-Yagi antenna based on the classic Yagi-Uda theory has several advantages over many traditional antennas, such as wideband, low profile, light weight, high gain and ease of fabrication. This dissertation mainly focuses on the study of pattern reconfigurable quasi-Yagi antenna.After brief introduction of the development of reconfigurable antenna and basic theory of Yagi-Uda antenna, the dissertation presents five kinds of reconfigurable antennas. Each of the schemes consist of four elements of quasi-Yagi antenna, the results of simulation show that the impedance bandwidth ranges of the proposed antennas are all excellent, the main beam in the xoy plane can be shifted to one of four angles by controlling the states of switches, and the variation in gain within operating bandwidth is relatively small. The pattern reconfigurability can be achieved across the operating bandwidth as well as on the resonant frequency. This dissertation presents the design of the modified radiating element and feed circuit of the proposed antennas, respectively. The modified radiating element can increase the bandwidth of the proposed antennas. When the modified feed circuit is used, the antennas have not only smaller size and simpler structure but also better performance in terms of bandwidth, pattern, gain and FBR. Besides, some proposed antennas can achieve pattern reconfigurable, the other can achieve frequency and pattern reconfigurable. Some typicals are fabricated and measured. The simulation results are in good agreement with the measurement results for the measured antennas. The proposed antennas have the potential for modern wireless communication.