| Since the geniture of microstrip antenna, it has been deeply studied and widely developed with its forte of light weight, small size, low cost, planar construction and easy to integrate, etc. Presently, we have developed a variety of planar constructed printed antenna, for example, microstrip antenna, striplined slot antenna, cavity backed slot antenna and printed dipole antenna. The weak spots of the microstrip antenna are narrow bandwidth and low gain. Therefore one of our primary research on the microstrip antenna is that how to break through the bandwidth limitation and increase its gain. Recent years, the lamination technology as a way of increasing the bandwidth of the microstrip antenna and increasing gain, has caught more and more attention of vast researchers, and it has been developed to double stratum and triple stratum which are the main form of laminated microstrip antenna, and has derived to different shapes of multiple laminated microstrip antenna. So then what impact would happen to the function of microstrip antenna if keep on laminating. This issue is still a blank space in the laminated microstrip antenna research. This article bases upon this as its starting point, by reading numerous interrelated documents and books, designs two different kinds of laminated microstrip antenna, and compares their main parameters, attempts to find out the affection rule to the major function of the microstrip antenna by the lamination technology.Based on the introduction of the basic knowledge of microstrip antenna, this article works primarily on several aspects below.First, it particularly explains the fundamental principle of microstrip antenna, analytical method and design steps of the laminated microstrip antenna. The rectangular microstrip patch antenna as one of the most representative sorts of microstrip antenna, is constituted by the rectangular microstrip patch, media substrate and floorboard, this sort of antenna possesses a very strong advantage on mathematical research and design, easy to model and analyse, there primarily are vector law, aperture radiation law, cavity model and transmission line model, etc. However due to the structure of the double-layer microstrip antenna is quite complex. Some common method as transimission line method to analyse the single-layer microstrip antenna and cavity model theory are no longer applicable here, therefore we have to use the severe full-wave analysis to research. As we ensure the physical parameters of the laminated rectangular microstrip antenna, we are strictly in accordance with the parameters of the microstrip antenna to design, on the basis of center frequency, bandwidth, impedance characteristics, stricktly design in accordance with the design steps: first choose the proper media substrate and its thickness, we determine the specific inductive capacityεr of the media simultaneously when choose the media substrate and loss tangent angle tanδ, the choose of media could affect directly to the size of the microstrip antenna, weight, beam pattern, bandwidth, aerial efficiency; and then determine the width and length of the rectangular patch unit; third, determine the size of the media subtrate and feed method of the antenna; finally, the calculation of the input impedance. The calculation of the input impedance is the key step in the design of the antenna, it works as an important role to implement in the design and matching of the feed network.Secondly, simply introduced three-dimention electromagnetic simulation software which is highly applied and mentioned in this article---ANSOFT HESS 10.0. This software is the application of finite element method of tangential component, which is able to solve any three-dimentional radiofrequency and distribution of electromagnetic field of microwave devices, compute the loss brought by the material and radiator. By simulation through the HFSS software, we can directly get the result of the natual impedance, propagation coefficient, S parameter, electromagnetic field, radiation field and aerial radiation pattern of the design model. This software can widely applied to the design of antenna, feeder line, wave filter, multiplexor, power splitter, microwave circulator, photoconducting device and isolator and calculation of electromagnetic compatibility, electromagnetic interference and antenna layout and crosscoupling, etc.Third, based upon the basic knowledge of microstrip antenna, we design a sort of rectangular microstrip antenna with three layer construction, and then to integrate the professional three-dimentional electromagnetical simulation software-Ansoft HFSS 10.0, to simulate and optimize the result of the design, simutaneously, while in the process to ensure the parameter with HFSS software, to observe the variation circumstances of the antenna parameter followed with the antenna performance. The result of the analysis shows: the impedance bandwidth and aerial gain vary along with the thickness of the media and distance difference between the patches; the impedance bandwidth is affected by the thickness of the media. The thicker the media closest to the radiation patch is, the wider the bandwidth is. However the aerial gain could not be fully increased by just increasing the distance between the lamination, in contrast, it would be decreased. To integrate a variety of parameters. In order to optimize the antenna performance, the result of the design clearly shows; the center frequency of the this antenna f0=10GHz, natural impedance is 50?, on the parameter diagram s, while s=-10dB,Δf/f×100%=10.3%, the largest antenna gain G=7.758dB.Finally, on the basis of the three layer microstrip antenna, to design a four-layer construction microstrip antenna onwards, and to aquire the optimum efficiency of the four-layer microstrip antenna, the result shows: the center frequency of the four-layer microstrip antenna f0=10GHz , while s=-10dB, the relative impedance bandwidthΔf/f×100%=6.5%, the largest antenna gain G=10.08dB. to compare the mentioned three-layer, four-layer microstrip antenna and the single, double layer microstrip antenna integrately, come to a conclusion that the affection brought by the lamination to the main function of the microstrip antenna. The experiments show that: the lamination technology can be able to stretch the antenna impedance bandwidth and increase the aerial gain, also can improve the characteristics of the directional pattern of the microstrip antenna, the thicker the media closest to the radiation patch unit, the wider the impedance bandwidth of the microstrip antenna; the more the lamination is, the more the aerial gain is, and the directivity will be better, however, the side lobe of the microstrip antenna will be increased.In the experiment, we take the overall scan to get the optimal value of the overall function of the antenna, basicly the result of the research generally meet our expectation, there are many difficulty and problems to be solved while in the course of the research, for example, to adopt idealized design overmuch may not fully reach our expected purpose in practical application, for which we are required to work practically in the future design, to utilize the simulation software more efficiently. |
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