Design And Research Of Circularly Polarized Filtenna Based On Metasurface

In recent years,metamaterials have attracted attention because of their electromagnetic properties that are not found in nature.As a two-dimensional metamaterial with the electromagnetic property of in-phase reflection of plane waves in a specific frequency range,the metasurface structure can be used as both the ground of an antenna and a direct radiation unit(also known as a metasurface antenna(MSA)),which can break through the structural and performance limits of traditional antennas and bring new ideas to the research of antennas in wireless communication systems.With the development of wireless communication technology,the demand of space-ground-sea-integrated is also proposed.The satellite system of space-based network has higher performance requirements for antennas,and wideband,high gain,filtering response and circularly polarization have become the development trend of satellite antennas.Therefore,it is of high academic value and application value to carry out research on new metasurface structures and their applications in satellite antennas.The main work of this thesis can be summarized as follows:1.Researches on wideband multi-mode circularly-polarized(CP)MSA: A non-uniform polarization rotation metasurface structure is proposed.Combined with characteristics mode analysis(CMA),a wideband CP metasurface with multi-mode characteristics is realized.By using differential feeding technology,a CP MSA with wideband characteristics is achieved.Its impedance bandwidth is 25.9%,the axial ratio(AR)bandwidth is 13.2%,and peak gain is 10.4 d Bic.Compared with traditional uniform MSA,the proposed antenna has better bandwidth,gain.This part of work provides valuable alternative technical solutions for realizing wideband CP antennas.2.Researches on CP MSA with filtering features: A new filter balun structure is proposed,combined with the non-uniform polarization rotation metasurface structure then design a broadband CP MSA with the good filtering features.The proposed antenna covers 5G N79 band with a center frequency of 4.7 GHz,which achieves an AR bandwidth of 17.7%,and peak gain of 8.9 d Bic.The out-of-band rejection is 31 d B.This part of work provides a valuable alternative technical solution for realizing wideband CP filtering antenna.3.Researches on CP MSA array with filtering features: In order to achieve wider AR bandwidth,higher gain and better out-of-band rejection,the CP MSA unit with the above filtering response is extended to the array.A sequential rotary feed structure is adopted to build a new type of CP metasurface filtering antenna array.The working bandwidth of proposed antenna can reach 27.3%and the realized gain can reach 13.4 d Bic.A prototype of the proposed dual-wideband antenna was fabricated and measured.The results show that the proposed antenna array has wide AR,high gain and good out-of-band rejection.This part of work provides a valuable choice for realizing wideband CP filtering antenna array.