Multi Frequency Left And Right Circularly Polarized Antenna With Dense Frequency Band

Circularly polarized antenna is widely used because of its advantages in anti-interference and can be used as a receiving and transmitting antenna at the same time.The spectrum of co mmunication systems,as a kind of key resources,is facing ever-increasing shortage.How to maximize the co mmunication capacity under limited spectrum resources becomes the research topic in the academic.This thesis is devoted to studying the characteristics of circular polarization radiation in multiple frequency bands with each band working independently and small high-low center frequency ratio,which is of great significance.The contribution of this thesis is to discuss the multi frequency left-right circular polarization antenna with small center frequency ratios.Contents of this paper include:Firstly,research on multi frequency circularly polarized antenna at home and abroad in recent years is reviewed,and contributions of this work are presented.Secondly,a compact small frequency ratio multi frequency left-right circular polarization antenna unit is designed.Considering the frequency ratio,the method by stacking three-layer antenna unit is adopted,because the frequency ratio of stacked antenna can be adjusted arbitrarily in theory.The feed is the use a probe coupled to the top-layer of the unit through vias.Because of the independence of stacked antennas,each layer of patch can be independently designed and then centralized to adjust the impedance and axial ratio of the whole antenna.The theoretical analysis is carried out,and it is further adjusted by HFSS.The results are: the multi frequency left-right circular polarization antenna works at 1.17 GHz-1.18 GHz,2.68 GHz-2.7 GHz,3.18GHz-3.32 GHz.The VSWR in the three frequency bands is less than 1.5 and the axial ratio is below 3 dB with boresight radiations.Thirdly,based on the above multi frequency left-right circular polarization element,a 2×2 array with sequential rotation feed is designed,where the array spacing is explored under low mutual coupling.The basic principle of the sequential rotation technology is discussed.