High-performance Circular Array OAM Antennas Based On Meta-surface And Its Applications

With the rapid development of wireless communication technology,the contradiction between limited spectrum resources and the rapidly growing communication needs of human beings has become increasingly prominent.It is urgent to study new technologies to utilize spectrum resources more efficiently.Recent studies have shown that different modes of electromagnetic vortex beams carrying Orbital Angular Momentum(OAM)are mutually orthogonal to each other.With its orthogonality,multiple independent data streams can be transmitted in parallel in the same frequency band,which has great potential to improve communication capacity and spectrum utilization,and can effectively alleviate the shortage of spectrum resources.In radar applications,the OAM beams can provide an additional azimuthal resolution due to the rotational degree of freedom,which can be used in superresolution radar imaging and detection of spinning projects.Firstly,two modes of C-band(5.8-6 GHz)circular array OAM antennas are simulated,which can generate mode l=+1 and mode l=+2 OAM beams respectively.Secondly,Bessel lens and Fabry-Perot resonator based on meta-surface are designed to optimize the radiation performance of the OAM antennas.Then based on the simulation results,the above OAM antennas and the corresponding Fabry-Perot resonator are fabricated.The phase distributions of the planar electric field and the far-field patterns are measured in a microwave anechoic chamber.The measurement results show that the designed OAM antennas can generate mode l=+1 and mode l=+2 beams.And the corresponding FabryPerot resonator can improve the directivities of the OAM antennas without changing the characteristics of the OAM beams.Finally,the designed OAM antennas are used for application experiments in both target detection and wireless communication.The rotational Doppler effect of the OAM vortex beams is used to measure the rotational velocity of the moving object,which verifies the feasibility of target detection using the OAM vortex beams.Then,the communication experiment is carried out using the Universal Software Radio Platform(USRP),and the video signals modulated by FBMC are transmitted between the same mode OAM antennas.Communication experiments prove the orthogonality between different modes of OAM vortex beams,which lays a foundation for the application of OAM technology in communication systems.