Beidou Terminal Dual-frequency Circular Polarization Antenna Design

With the sharply development of Beidou navigation system,a variety of requirements were put out for the terminal antenna to achieve the goal of high precision and real-time positioning of the navigation system.The radiates were circular polarization signals of Beidou satellite navigation system,which equipped merits like anti-interference and strong signal reception capability,circular polarization are attracting much attention in the Beidou terminal antenna.The Beidou navigation system communicates with ground terminals,including uplink and downlink,which requires the dual frequency characteristics of the terminal antenna.Two terminal antenna used in Beidou system were designed by deep studying the characteristics of circular polarization and dual-frequency of microstrip antenna in this paper.The main contents of this paper are described n detail as follows:First,the basic theory of microstrip antenna were studied,including the radiation principle,the method of feeding and the method of realizing the characteristic of circular polarization and dual frequency.Secondly,in the process of design Beidou terminal antenna,the space mapping algorithm is used as the optimization subject,which not only ensures the accuracy of the result,but also consider the efficiency of optimization.The core idea of the space mapping algorithm is to optimize the antenna design by using the mapping relationship between the coarse model and the fine model,which optimized is the optimization of the simple coarse model rather than the complex fine model.In this paper,the aggressive space mapping algorithm and the response surface approximate space mapping algorithm are mainly studied,in which the aggressive space mapping algorithm avoid the shortcomings of the traditional optimization algorithms,and the mapping relationships based on the coarse model and the fine model need not to be linear.And with many variables,the optimization speed is also faster than the traditional algorithm,while the response surface method approximate space mapping algorithm is mainly for complex antenna,many antennas are difficult to find its rough model.Therefore,using Kriging difference response surface method to construct rough model can effectively improve the optimization speed of antenna,and the range of application is more extensive.Then,aiming at the difference of the above two optimization algorithms,taking the circularly polarized rectangular tangent microstrip patch antenna as an example,the above two methods are used to optimize the antenna.It's obviously found from the response surface approximate space mapping algorithm is more convenient and suitable for the complex antenna which is difficult to find the empirical formula.It can broad the scope of application of the space mapping algorithm effectively.Finally,two kinds of terminal antennas used in Beidou system are designed.O ne is a single-layer terminal antenna,the patch is printed directly on a dielectric plate,which can effectively reduce the thickness of the antenna,and the other one is a multi-layer microstrip antenna.Using two layers of dielectric substrate and adding air layer and foam layer can effectively widen the bandwidth of antenna.Both antennas are modeled in HFSS.The optimization design of two antennas is carried out respectively by using the response surface approximate space mapping algorithm the in chapter three.