Research On Metasurface And Its Applications In OAM And Lens Antenna

Metasurfaces,as two-dimensional forms of metamaterials,play an important role in technologies such as electromagnetic imaging,stealth,and communication due to their strong control over electromagnetic waves and low-profile structural advantages.In particular,metasurfaces have shown great potential and development space in the field of antenna technology.There are various ways to combine metasurfaces with antennas.Loading metasurfaces in the form of lens above antennas can improve the radiation performances of antennas and also can achieve many novel applications,which are attracting more and more attention from academia and industry.According to the combination method,transmissive metasurfaces can be divided into those based on single-layer or multi-layer dielectric plate structure.The former often has the advantages of low profile,low processing cost,and high reliability,and has achieved extensive research achievements.However,there are also some shortcomings,for example,it is difficult to simultaneously achieve multiple characteristics such as wide bandwidth,high transmission,and 0° ~ 360° phase shift coverage.In addition,how to further meet the next-generation network’s demands for higher frequency efficiency and reduce gain loss during beam scanning are also current research hotspots and difficulties.This dissertation focuses on these hotspots and difficulties and summarizes the main work and innovation points as follows:1.Research and design of wideband transmissive metasurface antenna based on single-layer dielectric plate.Based on the generalized Snell’s law and the idea of phase stitching,a set of new transmissive metasurface units is proposed,which overcomes the difficulty of simultaneously achieving wide bandwidth,higher transmission amplitude,and 0° ~ 360°phase shift coverage for transmissive metasurface units based on single-layer dielectric plate,and it can also maintain good transmission effect when the electromagnetic wave is oblique incident at a certain angle.Then,this dissertation successively studies and designs two different types of feeds.Based on the proposed metasurface units and one of the feeds,adopting optimization algorithm,and a broadband high-performance lens antenna based on a 1 dB gain bandwidth definition is proposed,simulated,and tested.Finally,using this set of metasurface units and another feed,a dual-polarized lens antenna is proposed.Simulation results show that the radiation performances of the proposed dual-polarized lens antenna are almost the same in two orthogonal polarization states.2.Research and design of wideband vortex beam metasurface lens antenna based on single-layer dielectric plate.Building on the previous research work,study was conducted to further improve the transmittance efficiency of the units.Another set of wideband and high-transmittance metasurface units based on single-layer dielectric plate was proposed,which can achieve electric field transmission amplitude greater than-1dB within the wideband.Subsequently,based on the theory of vortex electromagnetic waves,a wideband vortex beam metasurface lens antenna was proposed,and the distribution of its near-field amplitude and phase as well as the far-field radiation performances were analyzed.The designed vortex beam antenna can generate +1 order vortex beam with high purity within the wideband.Finally,fabrication and measurement were conducted to verify the accuracy of the design,and the measurement results were reasonably consistent with the simulation results.3.Research and design of orbital angular momentum generation and multiplexing based on circularly traveling wave antenna.A method of generating and multiplexing orbital angular momentum(OAM)based on circularly traveling wave antenna is proposed.Multiple circular structures can be integrated coaxially under a shared aperture to effectively generate multiple OAM modes.The principle of OAM generation by circular current and the order of OAM on each polarization component are theoretically analyzed in detail.Simulation and experimental results of the near-field and far-field confirm that the proposed antenna can generate OAM modes with high purity,which is consistent with the theoretical analysis.The OAM multiplexing antenna proposed has the advantages of simple feeding and easy integration without complex feed network,and has great potential for application in wireless communication systems.4.Research and design of multi-beam metasurface lens antenna.In order to improve the gain of the multi-beam antennas and reduce the gain loss of beam scanning,three different design schemes are proposed by loading a metasurface lens over the multi-beam antennas.The corresponding low-profile multi-beam metasurface lens antennas are designed respectively,and their simulation analysis and comparison are carried out.Compared to the monolithic single-focus scheme and the monolithic multi-focus scheme,the block multi-focus scheme divides the lens into three regions according to the intensity distribution of the electric field on the surface of the lens when different beams are irradiated.By compensating the phase shift required by the corresponding beams in different regions,the beams gain is improved and the beam consistency is maintained.5.Research and design of wide beamwidth antenna.To reduce the ratio of focal length to aperture diameter of the lens antenna(the half angle of the beam from the feed to the edge of the lens will be increased)and achieve a relatively uniform amplitude distribution on the aperture surface,three wide beamwidth antennas based on gradient slot line antenna are proposed,each with different beamwidth widening effects.They can respectively achieve the following effects:(1)Broadening of the antenna 3 dB beamwidth in the E-plane by over 3 times within the wideband.Compared with the published similar work,it has the advantage of wider bandwidth under the premise of achieving similar beamwidth widening effect;(2)Widening the antenna 3dB beamwidth in the H-plane by over 2 times within the wideband;(3)Achieving simultaneously beamwidth widening effect in all azimuth planes,with a similar widening magnitude.These three antennas can achieve significant beamwidth widening effects.