發(fā)布時間：2018-06-30 01:27

  本文選題：電波傳播 + 拋物方程��； 參考：《西南交通大學》2016年博士論文

【摘要】：近年來,復雜電磁環(huán)境中電波傳播問題的研究已成為國內外學者關注的熱點問題。構建復雜環(huán)境要素的可計算模型,并實現大區(qū)域復雜環(huán)境中電磁分布特性的快速仿真和分析,能為無線通信、電磁監(jiān)控、電子對抗等實際應用提供關鍵的數值模擬技術和數據支撐,具有非常重要的軍用以及民用價值。與已有的電波傳播模型相比,拋物方程本身就能體現電波傳播的折射與繞射效應,可以充分考慮不規(guī)則地表結構、非均勻媒質等復雜環(huán)境對電波傳播的影響,且其SSFT解法在傳播方向的網格步長幾乎不受波長限制,因此非常適合于大區(qū)域復雜環(huán)境中電磁覆蓋特性預測。本文基于拋物方程,對森林、粗糙海面等復雜地理環(huán)境的電磁建模方法以及拋物方程的高效網格模型、高效數值解法等進行了深入研究,這對于快速高效地求解大區(qū)域復雜環(huán)境中的電波傳播問題具有重要意義。本文主要研究工作如下：第一,基于拋物方程對森林、陡峭障礙物、粗糙海面等復雜地理環(huán)境的電磁建模方法展開了研究。根據森林環(huán)境的物理組成,應用兩相混合物折射方法改進了森林的等效拋物方程模型,與文獻實驗結果的對比驗證了該模型的有效性,在此基礎上,討論了森林的植物體積含量、重量含水量以及自由水鹽度對電波傳播的影響。為了計算陡峭障礙物的后向反射波,研究了雙向拋物方程方法,并采用射線跟蹤法對其正確性進行了驗證,在此基礎上,提出了雙向拋物方程的并行方法,并探討了其并行性能,結果表明,該并行方法大大提高了雙向拋物方程對障礙物間多次反射波的求解速度；針對室內垂直墻面、家具等對電磁波后向反射較大的問題,提出了Pade型雙向拋物方程模型,并應用該模型模擬了存在二棟雙層建筑物時室內的電磁分布特性。另外,在考慮海浪陰影效應的情況下,構建了粗糙海面的等效拋物方程模型,實例仿真了電磁波在粗糙海面環(huán)境中的傳播特性,結果表明,該模型能夠體現海浪陰影效應以及不同海面風速對電波傳播的影響。第二,提出了拋物方程的非均勻網格模型、多重非均勻網格模型以及亞網格模型等高效網格模型。首先,詳細探討了拋物方程水平網格步長的取值范圍,并通過對傳播空間的不同區(qū)域采用不同的網格劃分,構建了拋物方程的非均勻網格模型,與雙射線模型以及均勻細網格拋物方程的對比驗證了該模型的正確性和高效性,同時,應用該模型模擬了三維復雜環(huán)境中的電磁覆蓋特性,進一步證明了非均勻網格模型的優(yōu)越性。在非均勻網格模型的基礎上,結合坐標變換技術、網格插值技術等,提出了拋物方程的多重非均勻網格模型及其基于OpenMP的并行方法,并模擬了復雜環(huán)境中存在四個輻射源時的電磁分布特性,由結果可知,多重非均勻網格模型使得拋物方程能夠對三維空間中的多輻射源電波傳播問題進行求解,且其并行方法大大提高了多輻射源問題的求解速度。最后,針對大區(qū)域復雜環(huán)境中存在關鍵目標的電波傳播問題,提出了拋物方程的亞網格模型,并詳細闡述了亞網格模型的具體實現方案,通過與均勻細網格拋物方程進行對比,驗證了亞網格模型的高效性,在此基礎上,對大尺度海面環(huán)境中艦船區(qū)域的場分布進行了預測和分析。第三,為了提升拋物方程的求解速度,本文對拋物方程的高效數值解法展開了研究�；�于鏡像原理,提出了拋物方程SSFT解法的快速計算方法,與已有的奇偶分解法相比,拋物方程的求解速度得到了有效的提升。同時,研究了拋物方程的ADI解法,推導了自由空間以及邊界上的場所滿足的ADI差分格式,并基于OpenMP提出了拋物方程ADI解法的并行方法,通過對加速比、并行效率等的分析可知,并行方法大大加快了拋物方程ADI解法的計算速度。另外,為了高效求解大區(qū)域復雜環(huán)境中存在隧道等腔體環(huán)境的電波傳播問題,提出了將拋物方程SSFT解法和ADI解法相結合的高效數值解法,并闡述了結合解法的具體實現方案,實例仿真表明,與ADI解法相比,結合解法極大地提高了拋物方程對該類問題的求解效率,在此基礎上,采用該結合解法模擬和分析了大區(qū)域環(huán)境中隧道內部的電磁分布特性。第四,基于并行自適應結構網格應用支撐軟件(JASMIN)框架研究了適用于高性能仿真平臺的拋物方程并行計算方法,進一步提高了拋物方程的求解速度。通過將同一步進面劃分成多個網格片,并分配到不同的處理器進行運算,實現了拋物方程FD解法的并行計算,與理論解的對比驗證了并行方法及程序的正確性,同時通過實例分析了并行程序的并行性能,算例表明,拋物方程FD解法的求解效率得到了有效地提高,在此基礎上,模擬了某一電信基站天線在包含9棟規(guī)則建筑物的城市小區(qū)環(huán)境中的電磁覆蓋特性。針對大區(qū)域復雜環(huán)境中的電波傳播問題,研究了拋物方程SSFT解法在JASMIN框架上的并行方法,并實現了相應的并行仿真程序,實例驗證了并行方法及程序的正確性和高效性,同時,基于該并行程序,完成了典型綜合三維大尺度場景的一體化建模,并對包含土壤、森林、大氣波導等復雜環(huán)境因素的典型綜合場景中的電波傳播特性進行了預測和分析。
[Abstract]:In recent years, the research of wave propagation in complex electromagnetic environment has become a hot topic of attention of scholars at home and abroad. To build a computable model of complex environment elements and to realize rapid simulation and analysis of electromagnetic distribution characteristics in large area complex environment can provide the key to the practical application of wireless communication, electromagnetism monitoring, electronic countermeasures and so on. The numerical simulation technology and data support have very important military and civil value. Compared with the existing wave propagation model, the parabolic equation itself can reflect the refraction and diffraction effect of the wave propagation. It can fully consider the influence of irregular surface structure, non-uniform medium and other complex environment on the wave propagation, and its SSFT solution is used. The mesh size of the propagation direction is almost unrestricted by the wavelength, so it is very suitable for the prediction of the electromagnetic coverage in the complex environment of large regions. Based on the parabolic equation, the electromagnetic modeling method of the complex geographical environment such as the forest, the rough sea and the sea surface, the efficient mesh model of the parabolic equation and the efficient numerical solution are studied in this paper. It is of great significance to quickly and efficiently solve the problem of wave propagation in large area complex environment. The main research work of this paper is as follows: firstly, the electromagnetic modeling method of the complex geographical environment such as forest, steep obstacle and rough sea surface based on parabolic equation is studied. According to the physical composition of the forest environment, the two phase mixing is applied. The method of refraction improved the equivalent parabolic equation model of forest. Compared with the results of literature experiment, the validity of the model was verified. On this basis, the effect of plant volume content, weight water content and free water salinity on the wave propagation was discussed. In order to calculate the backward reflection wave of steep obstacles, the two-way throwing was studied. On the basis of this, a parallel method of bidirectional parabolic equation is proposed and its parallel performance is discussed. The results show that the parallel method greatly improves the speed of the two-way parabolic equation to solve multiple anti ejection waves between obstacles; for indoor vertical walls, furniture In the case of large backward reflection of electromagnetic wave, a Pade type bidirectional parabolic equation model is proposed. The model is used to simulate the indoor electromagnetic distribution characteristics in the presence of two double deck buildings. In addition, the equivalent parabolic equation model of the rough sea surface is constructed in the case of the sea wave shadow effect, and the electromagnetic wave is simulated in the rough. The propagation characteristics of the sea surface environment show that the model can reflect the effect of sea wave shadow and the influence of different sea surface wind speed on the wave propagation. Second, the non-uniform grid model of parabolic equation, the multi inhomogeneous mesh model and the subgrid model are proposed. First, the parabolic equation horizontal network is discussed in detail. A non uniform mesh model of parabolic equation is constructed by using different meshes of different regions in different regions of the space. The correctness and efficiency of the model are verified by the comparison with the double ray model and the uniform fine mesh parabolic equation. At the same time, the model is used to simulate the electricity in the three-dimensional complex environment. The characteristics of magnetic coverage further prove the superiority of the non-uniform grid model. On the basis of the non-uniform grid model, combining the coordinate transformation technique and the grid interpolation technique, the multiple non-uniform grid model of parabolic equation and the parallel method based on OpenMP are proposed, and the electromagnetic field of four radiation sources in the complex environment is modeled. The distribution characteristics can be seen from the results that the multiple non-uniform grid model makes the parabolic equation can solve the problem of the multi radiation source wave propagation in the three-dimensional space, and its parallel method greatly improves the speed of solving the problem of multiple sources. Finally, the problem of the wave propagation of the key targets in the complex environment of large regions is proposed. The subgrid model of parabolic equation and detailed implementation of submeshes model are described in detail. By comparing with the uniform fine mesh parabolic equation, the efficiency of the subgrid model is verified. On this basis, the field distribution of the ship area in the large scale sea surface environment is predicted and analyzed. Third, in order to improve the parabolic equation, In this paper, the efficient numerical solution of parabolic equation is studied in this paper. Based on the principle of mirror image, a fast calculation method of the parabolic equation SSFT solution is proposed. Compared with the existing odd even decomposition method, the solution speed of the parabolic equation is improved effectively. At the same time, the ADI solution of the parabolic equation is studied and the free space is derived and the free space is derived. The ADI difference scheme for the place on the boundary is satisfied and a parallel method of the parabolic equation ADI solution is proposed based on OpenMP. By the analysis of the acceleration ratio and the parallel efficiency, the parallel method greatly speeds up the calculation speed of the parabolic equation ADI solution. In addition, in order to efficiently solve the tunnel and other cavity environment in the large area complex environment, The problem of wave propagation is presented. A high efficient numerical solution is proposed, which combines the SSFT solution of parabolic equation and the ADI solution. The concrete realization scheme of the combined solution is expounded. The simulation shows that the solution efficiency of the parabolic equation is greatly improved by the method of solving the solution of the ADI solution. On this basis, the combination method is used to simulate the solution. The characteristics of the electromagnetic distribution inside the tunnel in large area are analyzed. Fourth, based on the parallel adaptive structure grid application support software (JASMIN) framework, the parallel calculation method of parabolic equation suitable for high performance simulation platform is studied, and the solution speed of the parabolic equation is further improved. By dividing the same step into multiple grids, the same step is further divided into multiple grids. The parallel computing of the parabolic equation FD solution is realized. The parallel method and the program are verified by comparison with the theoretical solution. At the same time, the parallel performance of the parallel program is analyzed by an example. The calculation example shows that the solution efficiency of the parabolic equation FD solution is effectively improved. On this basis, the calculation example shows that the solution efficiency of the parabolic equation method is improved effectively. The electromagnetic coverage characteristics of a telecommunication base station antenna in the urban residential area containing 9 regular buildings are simulated. The parallel method of the parabolic equation SSFT solution on the JASMIN frame is studied for the problem of the wave propagation in the complex environment of the large area. The corresponding simulation program is realized. The parallel method and the process are verified by an example. At the same time, based on the parallel program, the integrated modeling of typical integrated three-dimensional large scale scene is completed, and the wave propagation characteristics in the typical comprehensive scenes including soil, forest and atmospheric waveguide are predicted and analyzed.
【學位授予單位】：西南交通大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN011

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