Research On The Generation And Regulation Mechanism Of Circularly Polarized OAM Electromagnetic Wave

The highly informational age provides an effective way for human beings to obtain the latest and most comprehensive multimedia information.But,the requirements for the transmission rate of the signal and the transmission capacity of the channel are also stricter and higher.Recently,the orbital angular momentum(OAM)was investigated by researchers to improve the channel capacity of wireless communication systems due to its orthogonality,and its research in the field of radio frequency is in its infancy.The main content of this paper can be divided into the following two aspects:(1)A conical conformal patch antenna with high gain characteristics is proposed to generate circularly polarized OAM electromagnetic waves.It is designed at 2.4GHz.We analyze the principle of generating the OAM waves by this structure through the formula of radiation field,in which the feasibility of the structure has also been verified in simulations.In order to reduce the degree of divergence of the OAM waves in the transmission process,a horn structure is placed in the external of the structure,which can increase the gain and directionality of the antenna efficiently.And the influence of the horn structure on the performance of the antenna is investigated and discussed in details.Finally,the feasibility of the proposed structure is further proved by experiment.(2)A novel helix antenna is proposed for generating adjustable OAM modes.Firstly,the principle of generating OAM waves is analyzed through theoretical calculation.By reasonable designing the pitch and radius of the helix,vortex electromagnetic waves with continuous modes number can be generated,which is verified by HFSS.At the same time,aiming at the problem of low purity of the vortex wave radiated by single-arm helix,we propose a double-arm helical antenna with symmetrical structure to improve the uniformity of radiation field,so as to improve the purity of vortex wave and the purity of vortex waves of all the generating modes is above 80% by calculating.We also load the circular-ring disk,cylindrical cavity and the dielectric to reduce the height of the helix and increase the gain of the antenna.Finally,the feasibility of the proposed structure is further proved in experiments.