The Cylindrical Coordinate Parabolic Equation Method Of Radio Wave Propagation And Its Application

With the rapid development of modern electronic technology,electromagnetic wave has become an important way of information transmission in wireless communication system.However,radio wave propagation in the troposphere is easily affected by mountains,hills,buildings on the surface,rough sea surface and complex meteorological environment,and its propagation characteristics will change significantly,which will affect the performance of wireless communication system.Therefore,the analysis and prediction of electromagnetic situation in complex environment based on geographic information is of great significance in practical engineering application such as radar long-distance target detection,identification and tracking,improving the performance of wireless communication system,realizing efficient utilization of spectrum resources and building a more perfect radio environment map.Parabolic equation method of wave propagation is derived from the approximation of wave equation and is a deterministic model of wave prediction.Compared with many prediction models of radio wave propagation,it can not only deal with the refraction effect of media,but also take into account the diffraction effect brought by irregular ground objects,so it is convenient to carry out integrated simulation of meteorological conditions and irregular ground environment.Combined with the Split Step Fourier Transform(SSFT),it can realize the fast solution.the calculation accuracy and efficiency are very high,which is very suitable for the prediction and analysis of electromagnetic characteristics in regional complex environment.Based on the parabolic equation method,this paper conducts visual analysis of radar electromagnetic energy,studies the coverage range of shipborne radar at sea,and carries out in-depth research on the modeling of regional real urban environment and its radio wave propagation characteristics.The main work contents of this paper are as follows:Firstly,the three-dimensional Cartesian coordinate parabolic equation(3DPE)method is derived in detail,and the SSFT solution form of the Feit-Fleck wide angle parabolic equation is obtained.The setting of the initial field and absorption boundary conditions are also introduced.Besides,the forward parabolic equation method in cylindrical coordinate(CPE)is derived and studied for the limitation of the traditional parabolic equation in horizontal section.By using the orthogonality of trigonometric functions,the excitation coefficients of each wave propagation mode are solved,and the stepwise iterative algorithm of the CPE is realized by combining the SSFT,and the correctness of the model and the omnidirectional characteristics of the azimuth plane are verified by numerical examples.Secondly,radar energy three-dimensional(3D)visualization and coverage analysis based on CPE.the three-dimensional visualization method of radio wave energy is studied.The image map and elevation map of the calculation area are extracted from the digital map,which are converted into grid data corresponding to the CPE.At the same time,the spatial electromagnetic field distribution at different sections is calculated and displayed in the threedimensional real geographical environment.Numerical examples are given to demonstrate the effectiveness of the proposed method.After that,the simulation analysis of the performance of CPE shows that the calculation accuracy is higher than that of quasi-three-dimensional parabolic equation(quasi-3DPE).Finally,it is applied to the complex geographical environment and the marine environment respectively to simulate and predict the electromagnetic state in the large area complex environment.On this basis,the coverage range of shipborne radar at sea is analyzed.Thirdly,the electromagnetic modeling of urban environment and the study of radio wave propagation characteristics.a prediction method of urban environmental radio wave propagation based on the combination of 3D solid reconstruction technology and CPE is proposed.The elevation vector data of urban buildings are extracted from the digital map,and the topological data structure of the stereolithographic file is established to realize the 3D geometric model reconstruction of urban buildings.At the same time,combining with the clustering algorithm and using the urban image information to classify the land surface environment,different types of land surface media are given different electromagnetic parameters,to achieve the real urban environment including building information and land surface media parameters of integrated electromagnetic modeling.Finally,the wave propagation characteristics in three-dimensional urban environment are simulated and analyzed by using the CPE.Fourthly,the study of urban environmental radio wave propagation based on two-way parabolic equation(TWPE)and CPE hybrid model.In view of the influence of buildings on the backscattering of radio wave propagation in complex urban environment,based on the traditional 3DPE,the Feit-Fleck wide-angle TWPE is derived in detail to simulate the backscattering of radio wave propagation.It is applied to the simulation analysis of the radio wave propagation in urban environment.Numerical examples show that the model can effectively consider the influence of urban buildings on the backscattering of radio waves.On this basis,CPE method is combined with TWPE method,and CPE is modified by TWPE bidirectional propagation characteristics,which makes up for the problem that CPE model cannot directly calculate bidirectional propagation.