Research Of Multi-frequency And Broadband Microstrip Antenna

In recent years, due to the development of communication systems with miniaturization, large capability, multi-function and intelligence, the research of multi-frequency and broadband micro-strip antenna has became interesting.In this paper, the author summarizes the methods of theoretical analysis of micro-strip antenna firstly, and expounds the theory of the finite element method. With the aim of implementing the characteristic of multi-frequency and broadband of micro-strip antenna, the author has done some researching work in several different aspects:(1)Implement the fractal concept to the design of antenna. Fractal antenna has shown the possibility of miniaturization and operating at various frequencies, because of the self-similar ability and space filling ability of fractal.Sierpinski fractal antenna has excellent multi-frequency property, but some disadvantages are going with, such as, the higher first resonance frequency, the worsen abilities of resonance depth and bandwidth. However, Parany Sierpinski fractal and its betterment can reform those disadvantages.(2) Implement the photonic ban-gap structure in the design of micro-strip antenna. Because of the periodicity of medium which composed the photonic crystals, the scattering curve of photonic crystals has a band structure, and there is a photonic band-gap(PBG) between bands like semi-conductor band-gap, which means the electromagnetism wave at some frequencies can't spread in any direction.In this section, the author researched the micro-strip antenna with PBG substrate. PBG substrate can restrain the surface wave in the patch of antenna, therefore, the radiation plus of antenna has a great improvement, and the return loss will reduce, the bandwidth will broaden. By comparing the analytic results of conventional patch antenna and patch antenna with a PBG substrate, we found the input loss of latter is 15.62dB lower, and its bandwidth is twice over that of the conventional patchantenna.(3) On the basis above, we researched the feasibility of fractal and PBG structure applied in the design of micro-strip antenna simultaneous. Because of the several resonance frequencies of multi-frequency antenna far from each other, we should guarantee enough bandwidth of PBQ which should cover all the frequencies.Because of the disadvantage of research condition, we did not manufacture the designed antennas. It is the biggest shortage of this dissertation.