Plane Spiral Orbital Angular Momentum Antenna Based On Dielectric Resonator And Its Application In Wireless Communication

With the development of the mobile communication technology,the demand for wireless transmission rates increases rapidly.The emergence of orbital angular momentum(OAM)brings the hope to solve the problem.Electromagnetic beams carrying different OAMs are orthogonal among each other,hence it can provide independent channels for the wireless communication to improve the channel capacity.In practice,the OAM carrying beams have some problems,such as beam divergence and central intensity darkness.These problems limit its application severely in long-distance communications.In order to solve these problems,our group proposed a novel kind of OAM carrying wave,termed as Plane Spiral OAM(PSOAM).This novel beam has traditional characteristics of OAM carrying beams.However,it spreads along the radial direction,which can solve the central intensity darkness problem in the far field,and the beams with different OAM modes propagate in the same direction.Therefore,the plane spiral OAM beam can provide a new idea for the OAM practical application.The small aperture OAM antenna not only enhances the advantages in the communication,but also makes it easier to be applied in mobile devices.In this paper,to solve the problem of large aperture and complex structure of the existing plane spiral OAM antenna,a small-size antenna based on the dielectric resonator is designed,and its application in wireless communications is explored.Based on the circular traveling-wave theory and the structure of the coaxial resonant cavity,the model of the dielectric resonator antenna is established.Through theoretical analysis,software simulation,manufacture and experimental verification,we find that the small-size dielectric resonator antenna can generate the PSOAM beam without adding any external auxiliary structure.The radiated wave propagates along the transverse plane and has spiral phase distribution,which owes the typical characteristics of the plane spiral OAM beam.Compared to the reported air cavity antenna with OAM mode equal to five,the aperture of the proposed dielectric resonator antenna is reduced by 81.64%.Plane spiral OAM beams propagate along the same direction and can be easily received.Different modes have different phase along the circumferential direction.Hence by utilizing these characteristics,the PSOAM beam is combined with the MIMO system.A new type of PSOAM-MIMO system is constructed,and its superiority to the traditional MIMO system is discussed.The channel capacity in the line-of-sight channel is firstly analyzed.Then the PSOAM-MIMO system is studied using the Spatial Channel Model(SCM)proposed by 3GPP,in which both line-of-sight channel and scattering channel exist it the same time under the urban microcell scenario.We find that the PSOAM-MIMO system has a larger channel capacity than the ordinary MIMO system in the near distance because of the line-of-sight channel.Plane spiral OAM wave is a special case of OAM carrying wave,and has the characteristics of the same main lobe direction,being easy to multiplex and simple to implement.The appearance of this small-aperture PSOAM antenna will help to introduce the PSOAM beam to other fields such as beamforming and Doppler analysis in the future and make OAM wave more potential in the electromagnetic field.