Research On Wideband Circularly Polarized Array And Feeding Network

With the development of the wireless applications,wideband circularly polarized array antennas have attracted great attention.In the process of designing broadband circularly polarized array,how to improve the circularly polarized antenna unit,design a broadband feeding network,and eliminate internal resonances are necessary problems to be solved.To achieve wideband high-gain circularly polarized arrays,this thesis focuses on the design of broadband circularly polarized arrays in two structures:tightly coupled array and sequential rotation spiral array.The main discussed contents are as follows:1)To solve the problem of insufficient bandwidth of tightly coupled array,crossed slot unit,gradient phase shifter and top-loading material three improvement measures are proposed.A 2.6-octaves tightly coupled top-loaded array antenna is designed and manufactured in this thesis.The antenna unit is an elliptical crossed dipole which uses a gradient three-quarter ring as 90°phase shifter.A dielectric layer is added on the top of the array to help improve the input impedance of the array and achieve the broadband circularly polarized radiation characteristics.This thesis provides the principle,detailed optimization process and test results to verify the effectiveness of proposed technologies.2)Aiming to solve the problem of internal resonances,two different absorbing structures are utilized to achieve a 5-octaves unidirectional spiral circularly polarized array.The improved structure of unit,sequential rotation feeding,wideband Wilkinson power dividers and slot-coupled phase shifters are used to improve bandwidth.Absorbing foam and a double-square-loop circuit analog absorber are added respectively between the radiation surface and mental ground to help achieve unidirectional radiation.The thesis provides detailed designing process and test results to prove the effectiveness of proposed measures.In a word,a tightly coupled crossed dipole array and a sequential-rotation spiral array are designed in this thesis.Two wideband circularly polarized arrays have been designed by applying measures such as top-loading,gradient structure,sequential rotation design.That's useful for the design of related antennas in the future.