Research On Propagation Characteristics Of The Vortex Wave In X-Band

Recently,with the development of the wireless communication technique,the requirement of channel capacity is increasing,Electromagnetic Vortex is attracting more and more attention because of its characteristics of carrying OAM(Orbital Angular Momentum)which has an infinite number of modes,and the modes are orthogonal to each other.It generates a new way of multiplexing after the time-division multiplexing,frequency division multiplexing and wavelength division multiplexing and provides a potential theoretical method for the expansion of channel capacity.It has a wide range of applications in the fields of communication and radar detection.The main contents of this thesis are as follows:Firstly,this thesis has made an introduction on the vortex electromagnetic waves,which is based on Laguerre-Gauss beam and the characteristics of phase singularity and OAM.In the vacuum,we takes advantage of Matlab to simulate mode distribution of field intensity and phase distribution of the vortex beam at different conditions.Secondly,the Kolmogorov atmospheric turbulence theory,the scalar field diffraction theory and the angular momentum spectrum decomposition theory are introduced.The factors influencing the atmospheric refractive index constant in the microwave band are introduced as well.And we construct the atmospheric turbulence phase screen with the power spectrum inversion method and Zernike polynomial method respectively.The advantages and disadvantages of the two methods are compared.Based on these methods,the atmospheric turbulence is applied to the propagation of the vortex wave.The influence of the field strength and the phase distribution is also calculated and analyzed.The distribution of OAM energy after propagation of specific distance is calculated and analyzed.Finally,the evaluation criteria——RMS(Root Mean Square)and PV(Peak to Valley),the degree of wavefront distortion,are identified.The algorithm of S-H wavefront detector is introduced.Based on the method of wavefront reconstruction,the truncation error and mode confusion in the wavefront reconstruction process using Zernike polynomial are simulated and analyzed.The correction effects on the OAM are analyzed by spectral decomposition method.