Generation And Synthesis Of Multi-Mode PSOAM Based On Gradient Metasurface

In the era of mobile Internet,people's demand for wireless communication is becoming more intense and comprehensive.How to rationally utilize limited spectrum resources and improve spectrum utilization needs to be solved for communication industry.As a possible solution,Orbital Angular Momentum(OAM)exhibits a great research value.However,OAM carrying waves possess phase singularity,inconsistent beam divergence for different modes and so on,which restricts its practical applications.In this context,the concept of Plane spiral OAM(PSOAM)was proposed.Different from traditional OAM beams(OAM propagating waves)propagating along the main axis,PSOAM beams for different modes all propagate along the same plane,so it's easy to realize multi-mode synthesis,and cleverly avoid different divergence problem.Multi-mode PSOAM synthesis can construct structured electromagnetic waves with diverse radiation patterns,hence exhibiting potential in radar detection and secure communication.The existing methods to generate PSOAM waves are against beam synthesis due to antenna size or radiation efficiency issues.Therefore,it is of great significance to explore a new method to realize multi-mode PSOAM synthesis and research characteristics of synthesized beams.In this paper,a new method to generate and synthesize multi-mode PSOAM waves is proposed.Using an annular configuration of gradient metasurface,it can transform incident OAM propagating waves to OAM surface waves,i.e.,generating PSOAM waves.When multi-mode OAM waves are incident on metasurface,multi-mode PSOAM generation and synthesis occur.The work of this paper provides a new idea for multi-mode PSOAM generation and synthesis.Based on theory of circular travelling-wave cavity,two circular cavity antennas are designed with OAM modes ±5 and ±3 at 15 GHz.Then an annulus configuration of gradient metasurface is emphatically designed,and antennas above are used as incident OAM sources for verification,afterwards the transformation from OAM waves to PSOAM waves is amply analyzed in theory.Furthemore,4-mode PSOAM synthesis with OAM modes ±5 and ±3 is realized in the lateral plane where metasurface is located,simulated radiation pattern is consistent with theoretical calculation.Then,by adjusting the feeding phases,synthesis pattern of modes +5 and +3 is used to realize beam scanning in the horizontal plane with a 360 degree range.