Research On Broadband Electromagnetic Wave Polarization Control Based On Metasurface

With the rapid development of communication and the advent of 5G,people have higher and higher requirements for electromagnetic wave propagation,especially in military fields such as satellite communication and antennas.Among them,in order to control the propagation of electromagnetic waves,research on the regulation and control of electromagnetic wave polarization is essential.Therefore,how to control the polarization state of electromagnetic waves simply and efficiently is very important in many military fields and modern communication fields.Metasurface is a two-dimensional metamaterial array plane with a sub-wavelength dimension.Studies have found that by designing its unit structure and arrangement,it can achieve polarization control of electromagnetic waves,and have the advantages of small size,wide application range,and easy integration.This paper proposes two polarization converters with ultra-wideband characteristics based on reflective metasurfaces.Besides,by optimizing the structure of the metasurface,three metasurfaces with different polarization functions were designed,which has the advantages of flexible design and diversified functions.In addition,based on the transmissive metasurface,a filter with wide-band characteristics is proposed,which achieves very good filtering performance.The specific research content is as follows:1.Firstly,the related electromagnetic theory of polarization conversion is studied,and the principle of polarization conversion of reflective metasurface is analyzed.On this basis,two cross-polarization converters with ultra-wideband characteristics are proposed based on reflective metasurfaces.Simulation and corresponding experimental results show that the two metasurfaces achieve high-efficiency cross-polarization conversion in the frequency bands above 20 GHz and 14 GHz,respectively,and the polarization conversion rate(PCR)is approximately 95%.It has important application value.2.Three kinds of polarization conversion metasurfaces with excellent characteristics are proposed.The first metasurface can realize the function of linear-circular and linear-cross polarization conversion.In the Ku-band,it can convert the incident linear polarization wave into a right-hand circular polarization wave,and the-3dB bandwidth reaches 5.35GHz(12.95-18.30GHz).In the frequency range of 25.50-30.42 GHz,PCR achieves approximately 100% of the linear-cross polarization conversion;The second is the polarization conversion metasurface with frequency shift characteristics.By changing the structural parameters of the metasurface,the blue shift of the spectrum of the operating frequency band from the X bandto the Ka band can be achieved.As the structural parameters change,the frequency band is getting wider and wider and the PCR is getting higher and higher.The minimum value of PCR in the 22 GHz band in the Ka band is about 95%.The third is the dual-band characteristic,high-efficient polarization conversion metasurface.These three metasurfaces greatly expand the diversity of polarization conversion functions and have broad application prospects in related fields such as antenna design,radar,and satellite communications.3.A band-pass filter with wide-band characteristics is proposed based on the transmissive metasurface.The filter consists of upper and lower metal patches and a dielectric substrate in the middle.Both metal patches are oval rings with a small opening.Simulation results show that the filter can achieve excellent filtering performance in the Ku-band,the-3dB band is 9.2-15.42 GHz,and the relative bandwidth is 50%.In addition,the filter has the advantages of simple structure and easy debugging characteristics,and has important applications in engineering devices.