| This dissertation, connected with 973 project, cooperation of baseband and antennas , is focused on the research of broadband planar fractal antennas. And several schemes of UWB and frequency-reconfigurable antennas are presented in this dissertation. This work provides good basis for the future work. The dissertation briefly discusses the mutual coupling among antennas, which provides good basis for the future work.The dissertation briefly introduces some producing background and research status at home and abroad about the fractal antennas and EMC. Then, the basic theory and related technology of the antenna radiation is introduced, the theories about the microstrip antenna are introduced, such as the mechanism of the microstrip antenna radiation, the analytic approach, feeding methods, broadband technology, miniaturization technology and reconfigurable technology. Subsequently, the basic ideas and characteristics of fractal structure and fractal antenna, related knowledge about fractal antenna array and the development trend of fractal antenna are presented briefly.Firstly, through the theoretically analyze and numerical emulation, effect of parameters modification on cylindrical shape within the first-order fractal slot structure antenna is analyzed. One method which can widen antenna's bandwidths for 6 times is presented and validated through emulation. Thereafter, makes a preliminary exploration of the frequency-reconfigurable antenna. Based on the theory of frequency-reconfigurable antenna and broadband antenna structure, three MEMS switch are used. By changing the states of the switches, the antenna can work in three frequency bands, which extends the bandwidth indirectly. A fractal antenna array is designed based on the fractal antenna unites designed before in this dissertation, and also preliminary analyses the mutual coupling among unites of antenna array.At last, we give the summary of the research work and expect about the future work. |
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