Design Of Circular Polarization Antenna And The Array

With the progress of information technology,the communication system is developing towards the direction of high speed and large capacity,which poses a great requirement to the performance of antenna.At present,the narrow band liner polarization antenna is difficult to meet the needs of multiple communication,which makes broadband circularly polarized antenna receive more and more attention.The omnidirectional circular polarization antenna has gained wide attention in application of communications,radar,satellite positioning and other civilian and military fields because it can communicate with arbitrary polarizing target in all directions in the horizontal plane.Based on the application of base station antenna and the performance of circular polarization is easy to be obtained by using coplanar waveguide.This thesis focuses on the design of broadband circularly polarized antenna for mobile communication.The main contents areas follows:1.A circular polarization antenna based on coplanar waveguide feed is studied and designed.The antenna consists of a coplanar waveguide structure,a square ring slot patch and a cross patch.The feed microstrip line is directly connected to the slotted ring structure.Meanwhile,a vertical cross patch is added to the center of the square ring structure to attain wider the axial ratio bandwidth.A metallic strip of width 5 mm is protruded and on the side of the CPW structure to match the bandwidth of antenna.The measured results show that the relative bandwidth of the antenna impedance is 61.2%(1.7GHz-3.2GHz),and the relative bandwidth of the axial ratio is 47.2%(1.7GHz-2.75GHz).The antenna has stable pattern and gain in the whole operating frequency band,which can meet the current mobile communication of 2G/3G/LTE.2.Artificial magnetic conductor structure is added based on the above coplanar waveguide fed antenna.The AMC structure is loaded on the back of the antenna to realize the unidirectional radiation of the antenna.Compared with the conventional coplanar waveguide antenna,it has the characteristics of high gain and wide band.The measured results show that the relative bandwidth of the antenna impedance is is 68.2% for VSWR<2 from 1.82 GHz to 3.75 GHz and the relative bandwidth of the axial ratio is 53.8%(1.9GHz-3.3GHz).Stable gain in the operating band,which can cover the current 3G/ LTE and WLAN mobile communications.3.A omnidirectional circularly polarized antenna is designed.The antenna consists of a feed structure and a array element structure.Four circular polarized antenna array elements are conformal in the four sides of the cuboid.The designed feed structure is used to feed the four array elements in equal amplitude and in phase,so as to realize the omnidirectional radiation of the antenna.The simulation results show that the operating bandwidth of omnidirectional antenna is 2.1GHz-2.6GHz and bandwidth of axial ratio is 2.07GHz-2.52 GHz.In summary,the two broadband circularly polarized antennas are designed to meet the requirements of the current communication system,and a omnidirectional circularly polarized antenna is simulated,which provides reference for the design of omnidirectional antenna.