| This dissertation, connected with 973 project,"cooperation of baseband and antennas", is focused on the research of pattern-reconfigurable planar fractal antennas. And several schemes of pattern-reconfigurable antennas are presented in this dissertation. This work provides good basis for the future work.The dissertation briefly introduces some producing background and research status at home and abroad about the reconfigurable antennas and fractal antennas. Then, the basic theory of the antenna radiation is introduced, the theories about the microstrip antenna are introduced, such as the mechanism of the microstrip antenna radiation, two methods based on transmission line model and cavity model, which are used to analyze the microstrip antenna, and the feeding methods of microstrip antenna. Especially, recent development of wideband and miniature microstrip antennas is presented. Subsequently, the basic ideas and theory of fractal structure and fractal antenna are presented briefly.Firstly, three schemes of pattern reconfigurable Hilbert patch antenna are presented by introducing the new patch structure. By switching the states of the antenna, the radiation beams can scan in the E-plane in the upper space. Then, the analyses of dielectric constant and dimensional of dielectric substrates on antenna performance are given. The new antennas have strongpoint thereinafter: high frequency bandwidth, low frequency, simple making and good performance.Secondly, the deeper study in the research of Hilbert patch antenna is done by introducing another patch structure. At last, we introduced several different measures to improve the performance of antenna. The new antenna's relative bandwidth is risen from 11.8% to 87.3%, and resonant frequency is reduces 1.49GHz and 2.14GHz. And the testing result of the experimental sample is agreement with the simulated results.At last, we give the summary of the research work and expect about the future work. |
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