| The gain and bandwidth are two important parameters of microstrip antennas, and themethods of enhanced gain and improved bandwidth in X band (11GHz～13GHz) arestudied mainly in this thesis. Firstly, the transmission-line model is used in the analysis ofaperture coupled microstrip antenna, and the equivalent circuit and calculation formulas ofit are deduced. Secondly, based on the analysis of micristrip slot antenna, using the cavitytheory, combined the time-harmonic field type of Maxwell's Equations, the distributionexpression of electric field in the interior of the cavity and the coefficients of theexpression are generated. Then, based on the spectral domain approach, with the MixedPotential Integral Equations (MPIE) and Complex Images, combined the dyadic Green'sfunctions, a briefly analysis has been done about the aperture coupled microstrip patchantenna, the expressions of radiation fields in the regions of radiation patch and microstripfeed network have been generated, thus the universal method for different electric currentand magnetic current distribution is provided.Due to the single microstrip patch antenna is a kind of standing wave antenna, anarrow bandwidth is resulted. To improve its bandwidth, a simple rectangular aperturecoupled microstrip antenna with three layers is introduced firstly, and a bandwidth of12.25% is obtained based on the analysis of the software of HFSS, ADS in thisthesis. Secondly, bandwidths of 13.70%, 13.36% are obtained separately by using twokinds of improved slot structures. Thirdly, based on the proposed design of aperturecoupled microstrip antenna above, a structure similar to the horn antenna is designedaround the single radiation patch element, and the simulated result indicates a 4.64dBenhanced gain has been achieved by the structure, while the basic characteristics remainthe same as the antenna without the dielectric adding.At last, we summarize the research of the thesis and propose some needed improvedproblems ulteriorly. |
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