Research On Wireless Signal Polarization Conversion Technology Based On Metasurface

Polarization is one of the basic properties of electromagnetic waves.It has a very important application in the field of wireless communication.So,how to control the polarization direction of electromagnetic waves simply and efficiently has always been a hot research topic in the field of electromagnetic waves.The use of metasurface to design polarization converters provides new ideas for research in this field.The metasurface is an artificial electromagnetic structure composed of two-dimensional unit structures arranged periodically.By designing different unit structures to realize the function of modulating the Polarization mode of incident electromagnetic waves.It has the advantages of small size and easy integration with other devices.In this paper,a transmissive and a reflective polarization converters are designed for the Ku-band,which realize the conversion of the incident Linear polarized electromagnetic waves to its orthogonally polarized electromagnetic waves.A new type of antenna with low radar cross section(RCS)is designed by combining the reflective polarization conversion metasurface with the microstrip antenna,which provides a new idea for reducing the RCS of the microstrip antenna.The main research contents of this paper are as follows:Firstly,the polarization transformation theory of metasurface is analyzed.Then a transmissive linear polarization conversion metasurface for Ku-band is proposed,and its cell structure,surface current and equivalent circuit are analyzed.It is shown by simulations and experiments that it converts the vertically incident electromagnetic waves with x-polarization into the transmitted electromagnetic waves with ypolarization from 12.5 GHz to 17.5 GHz,and the transmission polarization conversion ratio reaches 90%.The principle of polarization conversion of reflective polarization conversion metasurface is analyzed,and a reflective linear polarization conversion super-surface for Ku-band is proposed.It consists of a double 'E' metal structure on the upper surface,an intermediate dielectric layer and a metal back plate on the lower surface.It has an anisotropy that allows the normally incident electromagnetic waves with x-or y-polarization to be converted to its the cross-polarized reflected waves.Simulations and experiments show that it has a working bandwidth of 12 GHz to 18 GHz and covers the Ku band.Combining the polarization conversion metasurface with the microstrip antenna achieves Wideband RCS reduction of the microstrip antenna.A low-RCS metasurface which uses a reasonable design of the polarization conversion metasurface distribution to control the energy of the scattering is constructed and combined with a conventional microstrip slot antenna to results in a significant reduction in its RCS of the antenna between 11 GHz and 18.5 GHz.At the same time,it does not reduce the radiation performance of the antenna.It provides a new idea for the application of polarization conversion metasurface.