Application And Visualization Of Parabolic Equation Method In Typical Large-Scale Geographical Environment

In the process of promoting social modernization with informatization,wireless communication is of great significance both in military and civil fields,and the accurate prediction of radio wave propagation is the premise and guarantee to improve the quality of wireless communications.Due to its efficient as well as stable numerical solution and its advantages of predicting propagation characteristics of electromagnetic wave in complicated environments,such as flat ground,sea surface,atmospheric duct and so on,the parabolic equation(PE)method has been favored by scholars at home and abroad in recent years.Addressed on the problem of radio wave propagation in typical large-region environment,this paper studies the application of the PE method in terrestrial and ocean scenarios.Besides,a system for radio wave propagation prediction is also developed.The main contributions are as follows: 1.Starting from the wave equation,the narrow angle parabolic equation(NAPE)model and the wide angle parabolic equation(WAPE)model are established and then solved by the split-step Fourier transform algorithm.The initial fields in the NAPE method and the WAPE one are derived by using the Green function method which is more accurate and general.In order to solve the equation quickly,the sine transform and the cosine transform are introduced to replace Fourier transform when the lower boundary is perfectly conducting.On the other hand,when the impedance boundary condition is considered at the lower boundary,the specific solving steps of the improved discrete mixed Fourier transform is also given.2.For propagation problems over terrains,the four commonly used terrain methods are compared and analyzed.In order to solve the problem that the piecewise linear shift map method is not applicable when the terrain slope is large enough,a terrain adaptive algorithm is proposed in this paper,which can be applied in any actual terrains in the premise of ensuring high accuracy.And on this basis,a two-way parabolic equation model is then discussed.In addition,a terrain extracting method is also put forward to obtain two-dimensional terrain profile from digital elevation models and combined with the terrain adaptive algorithm,which improve the practical value of PE method.3.For propagation problems over sea,in order to study the abnormal propagation in atmospheric ducts,the PE models dealing with smooth sea surface and rough sea surface are established respectively.Besides,some influencing factors,such as antenna height,waveguide height,frequency,wind speed and so on,are discussed in detail.Considering that the traditional model is inapplicable when the wind speed is large and the height of the transmitting antenna is low,a PE model based on the actual sea spectrum is proposed,which can fully deal with the geometry of the sea surface.Moreover,the propagation in island environment is also studied,and the various influencing factors are discussed and analyzed.4.A prediction system is developed,which integrates terrain-data processing,man-machine interface,PE solving,and results visualization.The system makes it possible to predict the propagation characteristics in typical large-region environment fast and accurately.