Study On The ADD-PE Method And Its Applications For Radio Propagation Problems In Large Geometric Environment

With the rapid development of the wireless electromagnetic technology,the electromagnetic signal becomes more complex and time varying,since the rapidly increment of the wireless equipment such as modern radar,navigation and positioning,wireless communication,electronic warfare and other wireless systems,thus the EMC between devices becomes more prominent.In addition,many effects such as the scattering,refraction and diffraction are caused by the complex geometric and meteorological environment,the electric distribution is significantly influenced during the propagation process.In order to realise the spectrum management,wireless channel prediction,blind sight prediction or reliability analysis for the large-scale geometric environment,the propagation prediction algorithm with high computational efficiency and high reliability is required.It provides an reference or theoretical support for the rational allocation and performance optimization for the equipments.In recent years,the numerical model of radio propagation has become an important research topic.Among them,the Parabolic Equation(PE)model is an effective simulation method for the wave propagation,which can satisfy the simulation requirements for the most electromagnetic engineering problems.By dividing the propagation region into several planes,the refraction and diffraction terms are considered respectively in the spatial or the angular spectrum domain,the step size for the propagation direction could be far greater than a wavelength,thus it was widely used for the large-scale environment.However,the traditional parabolic equation model still has some shortcomings.In the Cartesian coordinate system,the reflection coefficients of electromagnetic waves are often different on the transverse and the longitudinal boundaries,while the traditional SSFT solution uses the global basis to describe the space field,so it is difficult to deal with the irregular boundary or different types of boundary conditions.Besides,the numerical amount becomes very large for the long-range transient propagation problems.In the tunnel environment,the shape of the cross section,the electrical parameters of the tunnel wall and the tunnel direction will have a great influence on the wave propagation,and the traditional parabolic equation is difficult to analyze these effects.In order to solves the problems mentioned above,this paper studies the numerical efficient solution for the parabolic equation model,the time domain parabolic equation model and the modified model for the tunnel environment,based on the traditional parabolic equation.An alternating direction decomposition method for three-dimensional parabolic equation model is proposed.By reducing the calculation dimension,the different boundary conditions in the marching planes are treated respectively,and the time domain parabolic equation model is proposed also,thus the solving number of frequency bins and the sampling points in the time domain are reduced,by the method of amplitude-phase separation and the envelope simulation.Finally,the SSFT method in tunnel environment is improved to consider the influence of the cross section of the tunnel,the electromagnetic parameters of the walls and the actual tunnel direction on the wave propagation.Besides,the initial field calculation of radiation source and modeling model for the complex propagation scene are also studied.The main contents of this paper are as follows:First,the information import and scene modeling part of the parabolic equation are improved.The electromagnetic modeling technology of the radiation source based on the parabolic equation model is studied.According to the latitude and longitude,the height of the arrangement and the attitude of the carrier,the far field and the initial field is calculated so as to characteristic the real antenna in the parabolic equation model.Besides,the digital elevation map reading and its correspond interpolation methods are explored,and the adaptive recognition of digital image map is introduced.In addition,a simple outfield test platform is designed and built,thus the parabolic equation model is verified by field measurement.Second,an alternating direction decomposition-split step Fourier transform(ADDSSFT)is proposed for the three-dimensional parabolic equation model.Through the decomposition of the diffraction factor,the marching is decomposition in rows approximately,then,the solve order of the parabolic equation is exchanged,so as to realize the acceleration of parabolic equation,and the numerical example verifies the performance of the proposed algorithm.The results show that,the proposed algorithm could cut the computation amount into half while keeping the RMS error in the same level,in applied for the radio propagation prediction in a large area environment,free space and half space RCS calculation,etc.At the same time,the parallel computation of parabolic equation is realized by combining graphics processor.This parallel scheme can significantly improve the computation efficiency of the parabolic equation,and make the parabolic equation algorithm be able to predict the radio propagation in large area in a quasi real-time way.Third,based on the parallel parabolic equation model,the propagation characteristics of the wide-band pulse are studied and analyzed.According to the characteristics of periodic pulse and mono-pulse,the applicable calculation method is deduced respectively.First,according to the characteristics of wave propagation in the regional environment,give new meaning to the amplitude and phase separation,then,through several numerical examples,the correctness of algorithm is validated and verified.Finally,combined with the radiation source modeling,digital map,parallel computing technology,perform a pulse propagation simulation in the real scene.Combined with FDTD algorithm,an outdoor to indoor electromagnetic simulation in large area is realized,to analysis time domain waveform in the inner side of the target.Fourth,based on the three dimensional parabolic equation algorithm,the propagation prediction model suitable for the arc tunnel environment is studied.In combination with space diversity technology,the location and phase of the transmitting antenna are configured and optimized to improve the link quality in the tunnel environment.The traditional parabolic equation is modified so that it can be used for calculation and analysis of the wave characteristics for the dielectric tunnel environment,then,according to the curvature radius,the tunnel can be divided into straight tunnel section and an arc-shaped tunnel section,the steering effect of the arc tunnel is accounted automatically,combining with the ADD-SSFT,achieve the radio wave propagation analysis for different tunnel structure.Finally,the radio wave propagation in the tunnel is calculated,and the parameters of the transceiver antenna and feed phase are optimized,and the optimization results are fed back to the design and optimization of the antenna pattern.the results show that the space diversity scheme in the tunnel is close to the theory lifting limit,could be used to eliminate the multi-path fading phenomenon for the environment effectively.