Design Of Conformal Microstrip Array Antennas

For missiles and other aircrafts,the conformal antenna can effectively solve the problem of limited installation space and reduce the impact of the installed antenna on the aerodynamic performance of the aircrafts,so it has been widely used.The microstrip patch antenna has the advantages of easy to be conformal with the carrier and low profile,which is suitable for installation on high-speed aircrafts.However,due to the narrow bandwidth of ordinary microstrip patch antenna,its application in conformal antenna field has been limited.Therefore,the broadband conformal microstrip patch antenna has become a research hotspot.This thesis focuses on the application of wideband microstrip patch antenna on the conformal phased array and conformal circularly polarized antenna.The main research contents of this thesis can be summarized as follows:1.Firstly,the related design methods and principles of microstrip patch antenna to achieve broadband,miniaturization and circular polarization characteristics are introduced respectively.Then,the radiation field solution and beam control methods of conical and cylindrical conformal phased array are described,which lays a theoretical foundation for the design of conformal phased array.2.In this thesis,the antenna element is designed by coupling feed using the microstrip strip,which not only expands the bandwidth,but also meets the requirement of easy to be conformal with the carrier.In order to reduce the coupling between the elements,the miniaturization of the antenna element is realized by loading the dielectric coating,and then a conical conformal phased array is designed based on the miniaturization element.In order to solve the problem of matching deterioration of the conical conformal phased array when scanning at a large angle,the matching layer is loaded to reduce the coupling effect between the elements so as to improve the matching.Considering the influence of conformal carrier curved surface,the phase compensation of the array is carried out.The finally designed conical conformal phased array can work in the whole X-band,and can realize one-dimensional large angle beam scanning on the elevation plane.Its beam scanning range at10GHz is 0°～111°.3.In order to meet the requirement that the conformal phased array can scan in the wide angular domain,a cylindrical conformal phased array with one-dimensional large-angle scanning characteristic is designed,which can scan within the range of±52°from the broadside direction at 10GHz.Then,the conical conformal arrays and the cylindrical conformal arrays are spliced,through the cooperative work of the two arrays,the conformal phased array can realize one-dimensional large angle beam scanning on the elevation plane,and the beam scanning range at 10GHz is±140°.4.To solve the problem of narrow bandwidth of conformal circularly polarized antenna,a microstrip conformal circularly polarized antenna element is designed in this thesis based on the theory of single feed circularly polarized antenna,which uses the coupled feed method to expand the impedance bandwidth.In order to broaden the axial ratio bandwidth,a sequential rotation feed network is designed by combining the inverse power divider with Wilkinson power divider,and then a cylindrical conformal circularly polarized array is designed based on the sequential rotation feeding network.Simulation results show that the antenna array achieves great circular polarization and broadband characteristics,and its relative operating bandwidth is 32.5%.