| With the improvement and perfection of the wireless communication system,the microstrip antenna is one of the key devices in the modern communication system.The advantages and disadvantages of the antenna performance will have a direct impact on the entire communication system.In order to achieve better communication quality and greater communication capacity,the circular polarization and multi frequency characteristics of microstrip antennas have become a research topic in recent years.In this thesis,the basic theory of microstrip antenna,including radiation principle,circular polarization and multi band working method,has been deeply studied.Based on the above theory,the S microstrip patch antenna and the T shaped slot double frequency circular polarized antenna are designed,and the simulation results and performance analysis of the two kinds of antennas are given.This thesis mainly includes the following aspects:(1)The basic theory of microstrip antenna is introduced,and the realization methods,advantages and disadvantages of circular polarization technology and multi frequency technology of microstrip antenna are studied.(2)A double frequency circular polarization antenna with low frequency is designed by single feed point feed.The antenna connects the rectangular loop and the double S parasitic cell by using short dipole,thus realizing the circular polarization and dual frequency characteristics of the antenna.The central frequency of S shaped microstrip patch antenna is 0.89GHz and 1.92GHz,and the return loss at its working frequency is lower than-10dB.(3)By simulating the radiation theory of circular microstrip antenna,the CNSS dual frequency circularly polarized antenna is simulated and analyzed.On the basis of this antenna,a circular polarization antenna with better circular polarization performance is designed for T slot double frequency circular polarization antenna.The antenna uses T shaped circular arcs with different orientations to achieve circular polarization.The aperture of the antenna not only reduce the size of the antenna but also realize the dual frequency circular polarization of the antenna.The frequency band of the antenna is 1.51 GHz-1.57GHz and 2.51GHz-2.67GHz.The echo loss of the antenna can reach-25.5dB and the axial ratio is lower than 3dB,and the result accords with the design requirement. |
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