| Metamaterials,as an artificial composite structure or composite material,have extraordinary physical properties that are not possessed by natural materials,and have received extensive attention in recent years.As a two-dimensional form of metamaterials,metasurface not only can control the direction of electromagnetic wave propagation,polarization state and beam direction,but also has great application value in antenna design.Therefore,based on the new metasurface structure,this paper studied and analyzed its basic characteristics,and made deep research on broadband low-profile circularly polarized antennas and arrays based on polarization-rotation metasurface.The main contents are as follows:1.The basic characteristics of metasurface are studied and the parameters affecting its reflection characteristics are analyzed.The polarization rotation characteristics of the polarization rotation metasurface(PRMS)are analyzed,and the parameters affecting the polarization rotation characteristics are analyzed.2.A novel low-profile dual-circularly polarized metasurface antenna(MSA)is proposed to realize wideband and widebeam right-and left-handed circular polarization radiations.The radiation structure of the antenna is constructed by an array of corner-truncated polarization-rotation metasurface(PRMS)cells,and fed by a new approximate cross-like slot to respectively provide two orthogonally linear-polarization(LP)coupling apertures on the same layer.Benefiting from wideband and widebeam polarization-rotation property of the PRMS cells,the proposed MSA can exhibit large axial-ratio bandwidths and large AR beamwidths at two polarizations.On this basis,combing with a sequential phase network,the proposed MSA is extended to construct a 2 × 2 dual-CP antenna array with larger impedance bandwidth(> 36),larger 3-dB axial-ratio bandwidths(>22.4%)and higher gains(> 11dBi).The work published a paper in the journal IEEE Antennas Wirel.Propag.Lett.(Chinese Academy of Sciences,2nd District),and published a paper on the international conference of the EI(International Conference of iWAT 2018).3.A new ultra-wideband circularly polarized metasurface antenna array is proposed,which can realize circularly polarized radiation with a bandwidth of 103.6%.Firstly,an ultra-wideband circularly polarized four-port feeder network is designed,which realizes the ultra-wideband phase shifting structure mainly through the weakly coupled transmission line,thereby providing four equal amplitude and phase sequence increments(0°,90°,180°,and 270°respectively)signals for the 2×2 antenna array.On this basis,the four-port fed circularly polarized feed network is combined with a 2 × 2 metasurface circularly polarized antenna array to construct an ultra-wideband circularly polarized metasurface antenna array.4.A novel dual-circularly polarized orbital angular momentum antenna is proposed.Based on the dual circularly polarized metasurface antenna array designed in chapter 3,the feed network is changed into a four-feed network with equal amplitude and phase,and combined with 2 × 2 circular poles of adjacent unit polarizations,a novel dual-circularly polarized orbital angular momentum antenna is proposed.The antenna can obtain wider impedance bandwidth and axial ratio bandwidth in both left-handed and right-handed circular polarization,and a more stable gain can be obtained.By observing the far-field phase distribution diagram of this antenna,it can be found that when the antenna is in the left-handed and right-handed states,the number of modes are l =-1 and l = +1respectively,and the feasibility of generating the orbital angular momentum beam by the dual-circularly polarized metasurface antenna array is confirmed. |
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