Research And Application Of Omnidirectional Linear To Circular Polarization Converter Based On Artificial Electromagnetic Structure

Omnidirectional circular polarization antenna combines the advantages of omnidirectional antenna and circular polarized antenna,and has a wide range of applications in mobile communications,multipoint communications,telemetry and remote sensing,positioning and navigation.The omnidirectional circular polarization antenna designed based on traditional methods has problems such as complex feeder network and narrow working bandwidth,which has limitations for the application of large-capacity communication and wideband communication,so it is of great significance to explore new technologies to design omnidirectional circular polarized antennas.With the increasing application of artificial electromagnetic structures in the field of polarization regulation,line-circular polarization converters based on artificial electromagnetic structure designs have the advantages of low profile and wide working bandwidth.At the same time,the development time of omnidirectional line polarization antenna is longer,the theory is more mature,it is easier to achieve broadband,and a wide variety of omnidirectional line polarized antennas can be applied to various specific scenarios.Therefore,based on the requirements of the project indicators,based on the artificial electromagnetic structure,the omnidirectional line-circular polarization converter working in the frequency bands of 8～12GHz and 4～8GHz is designed,and applied to the omnidirectional linear polarization antenna to achieve omnidirectional circular polarization radiation.The main research content and research ideas are summarized as follows:In the first stage of work,based on the artificial electromagnetic structure,the feasibility of omnidirectional line-circular polarization converters in the 8～12GHz frequency band was explored,and the design scheme was determined.First of all,a socket antenna with wideband characteristics is designed,which can operate in the frequency band of 6.79～23.1GHz(relative bandwidth of 109.1%).Secondly,based on the artificial electromagnetic structure,a polarization conversion unit with broadband characteristics is designed,which converts the u-polarized incident wave into a circularly polarized transmission wave in the frequency band of6.92～16.88GHz(relative bandwidth of 83.7%),which has a low profile and stable polarization conversion function in the large angle of incidence,based on the above unit to construct a quadrilateral omnidirectional line-circular polarization converter,which can convert the holographic polarization wave radiated by the sleeve antenna into an omnidirectional circular polarization wave.Finally,through joint simulation optimization,when the sleeve antenna is used in combination with the quadrilateral omnidirectional-circular polarization converter,the3 d B axis specific frequency band is 9.0～11.55GHz(relative bandwidth is 24.8%),and the coincident frequency band of the-10 d B impedance band and the 3d B axis specific frequency band is 10.66～11.55(relative bandwidth is 8.0%),which can be considered equivalent to an omnidirectional circularized antenna with an operating bandwidth of 8.0% when the sleeve antenna is used in combination with the quadrilateral polarizer.In the second phase of the work,based on artificial electromagnetic structures,the method of designing omnidirectional line-circular polarization converters in the 4～8GHz frequency band was explored,and a universal line-circular polarization converter with broadband characteristics was designed,and its versatility to different omnidirectional linear polarization antennas was discussed.Firstly,two kinds of antennas radiating omnidirectional vertical polarization electromagnetic waves are designed,and then a polarization conversion unit that converts ypolarized incident waves into circular polarized transmission waves in the frequency band of4.47～6.3GHz(relative bandwidth is 34.0%)based on artificial electromagnetic structures is designed,and a cylindrical omnidirectional line-circular polarization converter is proposed based on the above units,and the linear polarization waves radiated by the double conical antenna and the sleeve antenna can achieve omnidirectional-circular polarization conversion.When the double cone antenna is used as a radiation source,the 3d B axis specific frequency band is 4.04～5.68GHz(relative bandwidth is 33.7%),and the-10 d B impedance band fully covers the 3d B axis specific frequency band,that is,the dual cone antenna and the cylindrical polarizer can be regarded as an omnidirectional circular polarization antenna with a working bandwidth of 33.7%;when the sleeve antenna is used as a radiation source,the 3d B axis specific frequency band is 4.26～4.98GHz(relative bandwidth is 15.6%),-The 10 d B impedance band fully covers the 3d B axis ratio band,i.e.the sleeve antenna and the cylindrical polarizer can be considered as an omnidirectional circular polarized antenna with an operating bandwidth of15.6%.Finally,the actual products were processed and tested,and the test results were close to the simulation results,thus verifying the effectiveness of the designed antenna and the omnidirectional line-circular polarization converter.