Research On Circularly Polarized Wideband And Wide Angle Scanning Phased Arrays

Circularly polarized phased array is widely used in satellite communication and other fields because of its advantages of suppressing polarization mismatch,multipath effect and Faraday rotation effect.And it can realize electronically controlled scanning flexibly at the same time.Wideband and wide beam are important research directions of circularly polarized phased array radar in recent years.In addition to the impedance bandwidth and half power beamwidth,the axial ratio bandwidth and axial ratio beamwidth should also be considered.In this thesis,a series of researches are carried out in two directions: the wide-angle scanning circularly polarized phased array and the wideband circularly polarized phased array.The main contents of this thesis are as follows:In Chapter 1,the background and significance of the application of circularly polarized antenna are briefly introduced,and the research direction of circularly polarized phased array is proposed.Then,the development process of circularly polarized antenna to achieve broadband and wide beam is introduced in detail,which provides an idea for designing the element to make circularly polarized broadband phased array or wide angle scanning phased array.Finally,this thesis also introduces the research progress of circularly polarized phased array,and the research of it is still few,and most of them only study one-dimensional wide-angle scanning.Finally,the main contributions and innovations of this thesis are summarized.In Chapter 2,based on the analysis of the circularly polarized electromagnetic wave,the axial ratio and other parameters of circularly polarized antenna are derived.And the methods to realize circularly polarized are listed.At the same time,the basic method of wideband circularly polarized antenna is introduced.Then,the array factor formulas of equidistant linear array and planar array with uniform excitation are introduced,as well as the theory of grating lobes.This thesis introduces the pattern product theorem,which is the theoretical basis of active element pattern synthesis and aperiodic array design.In Chapter 3,a low axial ratio circularly polarized wide angle scanning phased array is designed.The element is a miniaturized small windmill-type wide axial ratio beamwidth circularly polarized antenna fed by octagonal series power divider.The 8 × 8array is designed based on sequential rotation technique.The array can achieve ± 60 °wide angle scanning with low axial ratio.Low sidelobe is realized by using genetic algorithm for pattern synthesis.In Chapter 4,two wideband circularly polarized phased arrays are designed.The first element is a microstrip patch antenna based on the substrate integrated waveguide slot structure,which is fed by a miniaturized feed network,achieving about 40% of the working bandwidth.A 4 × 4 polarized array using sequential rotation technique is formed.The second element is a dual circularly polarized ultra wideband antenna with high isolation,which is fed by a feed network composed of broadband miniaturized directional couplers,achieving more than 50% of the working bandwidth.An improved genetic algorithm is used to optimize the arrangement of aperiodic array.Finally,a broadband circularly polarized phased array with low sidelobe is realized.In Chapter 5,we review the work of this thesis and look forward to the next step.