Analysis Of Multi-mode OAM Wave Propagation And Antenna Design

In recent years,modern information and communication technologies have been developed with each passing day.Wireless communication technology has attracted more and more attention due to its portability and real-time characteristics.However,through research in the fields of time domain,code domain and space domain,the corresponding resource utilization efficiency has been close to the theoretical ceiling,and it is difficult to meet the demand for further explosive data capacity growth of wireless communication systems.Therefore,in order to break through the limitations of the existing resource capacity,the vortex electromagnetic wave carrying the orbital angular momentum as a new electromagnetic wave propagation mode has emerged.Due to the unique phase vortex distribution characteristics of the vortex electromagnetic wave,it has the ability to further improve the communication capacity,and it is expected to make breakthroughs in today’s communication technology.At the same time,due to the introduced vortex phase characteristics,vortex electromagnetic waves also have great potential in the field of detection.However,the current research on vortex electromagnetic waves is still not mature,mainly focusing on simple communication system construction and vortex electromagnetic wave antenna design,but the deeper principle study of vortex electromagnetic wave propagation and the systematic analysis of vortex wave source are still There is a lack of it.In this paper,the characteristics of multi-mode vortex electromagnetic wave propagation and the corresponding antenna design research are carried out around the above problems,which provides theoretical and physical support for the subsequent research and application of vortex electromagnetic waves.The research content of this thesis mainly includes the following four aspects:Analysis of vortex electromagnetic wave source and multi-mode vortex electromagnetic wave antenna design: Based on Maxwell’s equation,the two sources are derived from continuous and discrete source distributions,respectively,and the relationship between the source distribution and the generated vortex electromagnetic wave is given.mathematical model.A vortex electromagnetic wave can be excited by using a source of vortex phase distribution.Among them,the phase mode theory is used to decompose the radiation characteristics of the discrete source,and the relationship between the major vortex mode and other stray vortex modes is clarified.The compensation effect among these vortex modes is used to improve vortex mode purity.Further,based on the continuous source distribution,the vortex electromagnetic wave is radiated by the high-order resonant mode of the microstrip,and the multi-mode vortex electromagnetic wave antenna is designed by combining the multi-ring with the multi-layer feeding network(mode number l = ±1,±2,±3,±4).The vortex wave radiation capability of the multi-mode antenna is verified from both simulation and experiments.The application of the vortex electromagnetic wave is used to constructed radiation source basis.Analysis of vortex electromagnetic wave reflection and refraction characteristics: The mathematical model of vortex electromagnetic wave propagation in free space is constructed from Maxwell equation and Helmholtz equation,and the plane wave decomposition form of vortex electromagnetic wave and the relationship between plane waves and vortex wave is given.Combined with the Snell-Fresnel theorem and the plane wave decomposed by the vortex electromagnetic wave,the reflection and refraction problems of the vortex electromagnetic wave at the interface of the medium are transformed into the reflection and refraction of the decomposed plane wave,and the reflection and refraction of the vortex electromagnetic wave at the interface of the medium are given.The characteristics of the amplitude and phase change,and perfect the constraints of the decomposition analysis.Compared with the mode number of the incident vortex electromagnetic wave,the mode number of the reflected vortex electromagnetic wave is opposite and the mode number remains unchanged during the refraction.This analysis is extended to the propagation problem of multi-layer interface,and the single-layer dielectric board is taken as an example for analysis and simulation verification.Finally,using near-field system in the anechoic chamber,the experimental scheme is designed to verify the reflection and refraction characteristics of the vortex electromagnetic wave on the dielectric plat,and provide the theoretical basis for the communication and detection applications of the vortex electromagnetic wave.Focusing analysis and antenna design of vortex electromagnetic wave: From the mathematical model of vortex electromagnetic wave radiation and the decomposition of plane wave,the analysis of the divergence characteristics of vortex electromagnetic wave is given.The theoretical possibilities of focused vortex electromagnetic wave are discussed.With the focusing characteristics of the Luneberg lens and the Maxwell fisheye lens,the possibility of focusing the vortex electromagnetic wave is verified by constructing the plane wave with low divergence angle,and the relationship between the focus limit and the lens aperture is given.In addition,the characteristics of the lateral deflection of the metal reflecting surface are used to design the reflector antenna to focus on the multi-mode vortex electromagnetic beam,which is verified by simulations and experiments.Furthermore,combined with the high gain characteristics of the Fabry-Perot cavity antenna and the reflection and refraction characteristics of the vortex electromagnetic wave,a closed Fabry-Perot cavity antenna focused vortex electromagnetic beam is proposed,and the corresponding theoretical analysis and design conditions are improved.Finally,simulation verification has been carried out to provide a high-gain and low-divergence angle vortex source for long-distance applications of vortex electromagnetic waves.Long-distance vortex electromagnetic wave propagation experiment: For the long-distance diffusion characteristics of vortex electromagnetic waves and the increase of vortex phase plane,a method for measuring the vortex electromagnetic wave radiation characteristics under longdistance conditions is designed,and the vortex phase retention is tested.characteristic.The multi-mode vortex electromagnetic wave focused by the reflecting surface was firstly verified by the experimental scheme in close range,and then the long-distance propagation characteristics of the vortex electromagnetic wave were tested under different distances of 3.7km and 7.0km respectively.Properties that the vortex mode order under long-distance conditions remains unchanged are verified,which provides the possibility for long-distance application of vortex electromagnetic wave vortex phase.