| The GPS navigation system as an emerging industry has an important application value in the field of military and civilian,And the Beidou navigation system,independent research and management in China is in the stage of rapid development and gradually put in use.Circular polarized antenna for satellite navigation system is of great importance to research and applicable value,because of its circular polarized signals.As we all know,wide beam antenna with strong coverage power can receive satellites from all sides,it has great help for the precision positioning navigation system,especially for the developing Beidou of our country,for satellites in space is less and scattered distribution,beam width is particularly important.In order to capture the satellite signal with weak signal strength quickly,it often requires antenna has a certain low elevation gain.At the same time,we also need the antenna has a certain bandwidth,so as to cover multiple frequencies of the satellite navigation system,decrease the number of antennas,and make equipment more compact.Based on the Beidou navigation system as the research background,this paper firstly expounds the current situation and existing problems of the terminal antenna.Then introduces the basic parameters of the antenna,microstrip antenna and the basic theory of circular polarization microstrip antenna.Including radiation principle,feeding ways and its difference,the experience formula for calculating the size of the patch,polarization mode and so on.Finally,in view of the series of the problems,we put forward the following solutions:(1)In order to solve the problem of narrow band,this paper proposes a new way of feed back("L" type feeder).First,analyzing the implementation mechanism of broad band,According to some empirical formulas,we designed the initial model based on the feeding mode.By using high frequency structure simulation software HFSS to get the parameter performances of the antenna,we found it does not meet the design requirements.And by the analysis on the model,we know that its performances is mainly influenced by"L" type horizontal and vertical arm length and the influence of the thickness of the substrate,So we adopt the control variable method and using HFSS,in turn,discussed the "L"type horizontal and vertical arm length and thickness of the base board of the three parameters on the antenna's frequency points.Studying found that only the thickness of the base board reaches a certain value,the solution shows broadband obviously;And horizontal arm mainly controls the high frequency,the location point of the high frequency increases with the decrease of the horizontal arm;Vertical arm mainly controls the low frequency,the location point of the low frequency decreases with the decrease of the Vertical arm.Then,on this basis,the best dimension of the "L" structure is chosen,respectively,the design meets the requirements to work in the big dipper uplink and downlink frequency band antenna model.(2)In order to achieve the purpose of the wide beam,a wide beam antenna is studied.It's innovation lies in the dual-band theory into the normal microstrip antenna-microstrip dielectric antenna.Specific operation is the u-shaped slot is joined on the patch,the antenna on the basis of the wide beam can also achieve multi-band work,and low elevation gain also improve to a certain extent,this model structure is simply easily to operate.(3)In order to achieve the purpose of miniaturization and high gain,a 2*2 microstrip fractal antenna array is designed Specially,Namely using four port feeder.It combines fractal technology with array technology perfectly.then we can get high gain and miniaturization.The application of the fractal technology in addition to decrease the size of the model in a large extent,also played a beautification effect of the exterior of the antenna,Four units The mutual compensation between four units of the model can make the antenna gain a good circular polarization performance at the same time. |
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