| Antenna is the indispensable component of wireless communication system as the importantradio-frequency front device of transmitting and receiving electromagnetic wave. With the rapiddevelopment of personal communication and wireless networks, the antenna is developing intominiaturization, multi-band, broadband and intelligence in recent years. Microstrip antennas havesome features, such as small size, light in weight, low profile, easy to fabricate and able to beintegrated with microwave circuits, which makes the microstrip antenna become a research hotspotthese years. This paper aims to discuss the multi-band operation of the microstrip antenna and threenovel multi-frequency microstrip antennas are designed.First this thesis gives an outline of the present development situation of the microstrip antenna,as well as the study background and new development of microstrip antenna of miniaturization andmulti-band are refered. Then, this paper elaborates the basic theory and analytical approach ofmicrostrip antenna, including classical theoretical analysis methods and popular numerical methods.Besides, the present technological means of microstrip antenna of miniaturization, multi-band andbroadband are summarized.At last, three novel multi-frequency mirostrip antennas are designed with some technologies ofminiaturization, multi-band and broadband. The first kind of microstrip antenna, which is fed by thecoaxial-cable vertically on the undersurface, comprises a circle patch on which several slots areetched; the second kind of microstrip antenna fed by coplanar waveguide(CPW) is composed ofsquare-ring monopole and U-shaped patch; the third kind of microstrip antenna, with rectanglepatch and U-shaped slot loaded, adopts electromagnetic coupling feed and cuts window on theground.On account of these antenna structures, Ansoft Corporation’s electromagnetic simulation softwareHFSS is used for studying change of performance indexs along with the change of the antenna structureparameters. On the basis of these, when expected performance indexs are appearing, the antennastructure is determined and the parameters of design are obtained. According to the design parameters,the actual antenna is manufactured. Then the physical antennas are measured by vector networkanalyzer and the test results of return loss of the antennas agree well with the simulation results. Theantennas can work in 2.4/2.5/3.5/5GHz frequency band and the performance indexs meet requirementsin each frequency band, so they can be applied in some wireless communication system such as WLANand WiMAX. And they have certain reference value to the practical wireless communicationapplications. Finally, the content and the innovation of the research work are summarized, and the futureresearch work is proposed. |
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