Research On Butler Matrix And Circularly Polarized Antenna Array

With highway traffic carried is also growing, to maintain continuous flow ofhighway poses a challenge. In this case, Our ETC industry has great development. Areceiving and transmitting antennas as the front end of the ETC also has greatdevelopment. In this paper, a beam switching antenna based on butler matrix is designedas the antenna of ETC. This beam switching antenna can simultaneously control multiplelanes and reduce the sidelobe level.The development background and overseas research status of ETC and butler matrixare presented in the first. And based on the theory, the basic principle of linear array anddesign method of butler matrix is researched. The theory concludes transmission lines ofmicrostrip antenna, even and odd mode method of directional coupler, antenna arraypattern multiplication principle and Dolph-Chebyshev synthesis method principle and soon. Through theoretical study concluded microstrip antenna and array design methodsand structure principles of Butler matrix and the realization of the amplitude-weightedapproach. Through the study of theoretical knowledge for later design work to lay thefoundation.Then, a microstrip antenna work at5.8GHz is designed firstly and a linear antennaarray that contain eight antenna elements. The simulation method is used to calculate theS-parameters and the pattern of the antenna array. Then a constant amplitude distribution4-port butler matrix is designed. The butler matrix is used to as the feed network of theantenna array and the simulation results is given by the CST studio. At last, a amplitudeweighting8-port butler matrix is designed to reduce the sidelobe level of the antennaarray. On this basis, a new structure of8-port butler matrix is proposed. This newstructure8-port butler matrix can form four different direction beams and the sidelobelevel of each beam is lower than the situation of constant amplitude distribution. The newstructure Butler matrix has higher transmission efficiency.