Study On Wide Beamwidth Planar Endfire/backfire Circularly Polarized Antennas

The Modern satellite navigation and positioning systems often require antennas have a uniform amplitude response,so the antenna used must be able to achieve a wider circularly polarized beam.The purpose of this thesis is to design a wide-beam circularly polarized antenna with end/backfire characteristics,on the same time making the main beam of the antenna parallel to the plane of the antenna is located.The combined structure of 300° fan-shaped magnetic dipole and electric dipole is designed.In the progress of designing target antenna,the theoretical prediction,simulation model and physical measurement can be agreed with each other.The main research contents of this thesis are as follows:1.This thesis is devoted to the design of a planar circularly polarized antenna with a wide beam.The circular polarization is realized by the combination of the fields of the magnetoelectric dipole,and the fan-shaped magnetic dipole with a central angle of 300° and the structure is determined through theoretical analysis.The combined structure of the fan-shaped magnetic dipole and the "V"-shaped electric dipole can effectively broaden the circularly polarized beam.Finally,according to the discussion of the inherent boundary conditions of the antenna,it is determined that the coaxial feed can avoid the spurious radiation and the cross-polarization component excited.2.After obtaining the approximate parameters of the antenna,in order to obtain the best parameters of the antenna,the numerical calculation software MATALB is used.Ansoft HFSS is used to build the simulation model.On the same time,according to the optimization to make the antenna of 2.4GHz.Using the vector network analyzer and the near-field antenna test system to do the measurement for antenna samples,then compare the measured results with the simulation results of the antennas,and discussion the reasons for the large difference between physical measurement results and simulation results.3.Based on the original planar wide beam end-fired circularly polarized antenna,a back-fired circularly polarized antenna consisting of a 300° sector magnetic dipole and a curved electric dipole is designed.In the process of making antenna samples,different media samples with different dielectric constants were used.It was finally determined that the dielectric material with the dielectric constant of 1 could make the antenna object and the simulation model fit well.The expected wide beam circularly polarized antenna can be obtained by this design method.