基于改进地形重构的SSPE传播预测方法

针对复杂环境下电波传播预测分析难的问题,提出了一种基于地形重构的分步抛物方程(split-step parabolic equation,SSPE)传播预测方法.该方法采用具有广角传播因子且步长可变的双向SSPE解法,并利用基于改进地形重构的SSPE传播预测方法对真实地形的电波传播特性进行仿真分析和试验验证.与现有的电...     

基于PE模型的电波传播特性预测技术研究

PE模型已经被广泛地应用于电波传播特性预测技术的研究,并成为解决电波传播问题的主要工具。通过对抛物方程推导过程中由于对伪微分算子Q的处理而产生的误差进行分析,表明PE模型在预测小仰角的电波传播时具有很好的计算精度。对基于PE模型的电波传输损耗理论模型进行计算机仿真,得到电波传播损耗的理论计算值,通过与实测数据进行对比,验证了PE模型用于电波传播特性预测的正确性,并且对理论模型的计算结果稍微偏小的原因做了分析。     

抛物方程法在森林环境电波传播特性预测中的应用

为提高大区域森林环境电波传播特性预测的准确性,研究抛物方程（PE）法在森林环境电波传播特性预测中的应用,提出了基于抛物方程的森林模型。该模型采用PE法实现准确快速求解,考虑森林在垂直方向上的非均匀性,引入森林分层模型,将森林分为树冠、树干两个均匀有耗介质层,并根据森林区域的特性参数确定各有耗介质层的等效介电常数,相比于传统将森林等效为一个给定介电常数的均匀有耗介质层,能够更准确地描述森林对电波传播的影响。将其应用于三种常见绿叶林的电波传播特性预测中,仿真结果表明,该模型能够反映不同区域、不同植被种类的森林对电波传播的影响差异,有效预测大区域森林环境电波传播特性。     

几种抛物方程形式的相位误差分析

近轴近似是引起抛物方程(parabolic equation,PE)自身固有相位误差的根本原因.为选取适合目标场景中的最优PE形式,基于色散分析方法,推导了现有六种PE形式的色散关系,评估出折射率和传播仰角对各PE形式相位误差的影响,进而分析出对流层电波传播、水下声波传播、森林电波传播三种典型场景中各PE形式的精度.研...     

PE模型预测蒸发波导中电波传播损耗

针对电磁波在蒸发波导中的异常传播现象,研究了电磁波在蒸发波导中的传播损耗,其传播损耗是电波传播的一个重要概念,并受到广泛关注。抛物模型(PE,Parabolic Equation Model)作为目前研究电波传播的主要模型,通过与Two-ray模型的对比分析验证了PE模型的可行性,且PE模型计算电磁波的传播损耗时可以克服其他模型预测粗糙海面时的不足。仿真分析表明,电波在蒸发波导中传播时的损耗值比在标准大气中的损耗值要小。     

部分森林覆盖山区电波传播特性预测的快速算法

为提高部分森林覆盖山区电波传播特性预测的时效性,提出了一种基于宽角抛物方程(PE)的快速预测算法。采用PE通过分步傅里叶变换(SSFT)求解;在SSFT步进迭代过程中,根据传播路径上森林的等效介电常数、地形的起伏情况,动态选择PE的水平步长。通过对部分森林覆盖的不规则地形条件下的电波传播特性进行仿真,探讨了该方法的可行性和有效性。结果表明：相比于均匀大步长算法,该方法更准确;而相比于均匀小步长算法,该方法能够保证抛物方程的计算精确度,同时极大地提高计算效率。     

基于抛物方程的电波相位预测方法

针对大气波导和不规则地形等复杂环境下的电波传播相位预测,研究了基于抛物方程(PE)的相位计算方法,并通过与理想导体平面上自由空间条件下几何光学双射线模型计算的传播相位对比,对该相位计算方法进行了验证.在此基础上,利用PE方法计算的幅度和相位,研究了大气波导对脉冲信号传播的影响.     

基于分形的粗糙海面三维抛物方程模型及其应用

风驱海浪随机起伏变化是海面环境的典型特征之一, 而较大的风浪通常会给海面无线通信带来重要的影响.传统的抛物方程(Parabolic Equationmethod, PE)模型在预测粗糙海面的电波传播时, 未能充分考虑海浪的电磁散射以及阴影效应等.针对以上不足, 文中基于三维抛物方程, 引入动力学分形方法, 对传统的抛物方程模型进行了改进研究.相比传统的Miller-Brown近似方法, 改进后的预测模型能更好地反映出海浪几何特征对电磁波传播的影响.最后以舰载雷达的有效探测范围为计算背景, 对粗糙海面的电波传播特性进行了仿真分析, 结果表明了该模型在区域级海面环境电波预测的可行性.     

基于双向有限差分抛物方程法的海洋环境电波传播研究

采用双向抛物方程（two-way parabolic equation，2WPE）法来预测复杂海洋环境中的电波传播特性，用双向有限差分（two-way finite-difference，2WFD）法求解2WPE，考虑了海岛等不规则地形引起的电波后向传播和大气波导的影响，并在前向和后向电波传播预测中引入一种改进的分形海面模型来模拟起伏波动的实际海面边界，且能模拟海面的大尺度浪涌特性和毛细波细微结构特性.在典型的数值算例中，我们将采用改进分形模型处理海面边界时计算得到的双向电波传播因子和采用Miller-Brown模型处理海面边界时计算得到的双向电波传播因子进行对比和分析，数值分析结果表明，在相同风速条件下，采用改进分形模型处理海面边界时计算得到的双向电波传播因子波动更剧烈，能更准确地反映出实际起伏波动海面对电磁波传播的影响.     

基于柱坐标抛物方程的海上雷达覆盖范围研究

为预测雷达波在海面的全向传播特性,提出了基于柱坐标抛物方程(parabolic equation,PE)的电波传播模型,用于海上雷达覆盖范围的研究.从亥姆霍兹方程出发,推导出柱坐标系下的前向PE形式.再利用PE通解中三角函数的正交性,求解各电波传播模式的激励系数,结合分步傅里叶变换实现柱坐标PE的步进迭代算法,以预测电...     

基于双向抛物线方程电波传播分析的矩量法验证研究

求解复杂环境下的电波传播问题,双向抛物线方程(2W-PE)是一种常用、准确、高效的方法,但其计算精度的验证一直是一个难题.为了在介质地面和障碍物条件下验证双向抛物线方程的计算精度,提出一种利用矩量法(MoM)验证双向抛物线方程的计算方法.该方法首先引入抛物线方程和矩量法统一的波源设置,然后推导了场型格林函数和PMCHW...     

An Efficient Hybrid Parabolic Equation – Integral Equation Method for the Analysis of Wave Propagation in Highly Complex Indoor Communication Environments

An efficient, full-wave computational technique to investigate the electromagnetic wave propagation within a complex building environment, resulting from contemporary indoor communication systems, is proposed. Unlike a standard ray-tracing technique, this new methodology is based on the parabolic wave equation (PE), appropriately modified to deal with the extremely wide-angle propagation cases, encountered in a typical wireless system of this kind. It is also successfully applied to model the field in the presence of walls, doors or other penetrable structures, taking into account the exact geometric configuration of the environment under consideration. Next, the PE technique is significantly enhanced by an integral equation formulation, in which the computed field in the interior of the walls and other obstacles is used as a secondary equivalent current source and a corrected version of the electromagnetic field is recalculated in the whole indoor environment. This combined approach has all the advantages of a full wave method, does not call for a highly dense mesh, and it also has moderate requirements of computational resources.     

起伏地形双向抛物线方法的计算与验证研究

双向抛物线方法是复杂环境下电波传播计算中的一种重要方法,提出一种新的不规则地形下双向抛物线方程用于电波传播的计算方法,该算法在求解过程中记录了所有波源的历史路径,结合具体路径对双向抛物线方法进行相位修正,并在步进过程中,对不同极化下障碍物表面的边界条件进行了重新处理,对目前采用的阶梯模型进行了改进。在此基础上,提出使用矩量法来精确验证近距离不同极化下双向抛物线方法的计算精度。通过实例分析,证明了起伏地形下新算法计算的精确性。     

The study of the transmission of GHz waves.in the oceanic low altitude waveguide in the PEM-based gridded method

A parabolic equation method （PEM）-based discrete algorithm is proposed and is used to obtain the field distribution in the evaporation duct space. This method not only improves the computing speed, but also provides the flexibility to adjust the simulation accuracy. Numerical simulation of the wave propagation in the oceanic waveguide structure is done. In addition, the initial field distribution and progressive steps are determined. The loss model in the waveguide is solved through the numerical solution. By comparing the characteristics of the radio wave propagation in the duct and in the normal atmospheric structure, we analyses the radio transmission over the horizon detection in the oceanic waveguide.     

A three-dimensional parabolic equation applied to VHF/UHFpropagation over irregular terrain

The two-dimensional (2-D) parabolic equation (PE) is widely used for making radiowave propagation predictions in the troposphere. The effects of transverse terrain gradients, propagation around the sides of obstacles, and scattering from large obstacles to the side of the great circle path are not modeled, leading to prediction errors in many situations. In this paper, these errors are addressed by extending the 2-D PE to three dimensions. This changes the matrix form of the PE making it difficult to solve. A novel iterative solver technique, which is highly efficient and guaranteed to converge, is presented. In order to confine the domain of computation, a three-dimensional (3-D) rectangular box is placed around the region of interest. A new second-order nonreflecting boundary condition is imposed on the surface of this box and its angular validity is established. The boundary condition is shown to keep unwanted fictitious reflections to an acceptable level in the domain of interest. The terrain boundary conditions for this 3-D PE method are developed and an original technique for incorporating them into the matrix form of the iterative solver is described. This is done using the concept of virtual field points below the ground. The prediction accuracy of the 3-D PE in comparison to the 2-D PE is tested both against indoor scaled frequency measurements and very high frequency (VHF) field trials     

抛物方程方法的亚网格模型及其应用研究

该文在抛物方程非均匀网格技术的基础上,提出了抛物方程方法的亚网格模型,并给出了该亚网格模型的具体构建方法,以快速准确地求解大尺度复杂电磁环境中存在关键目标的电波传播问题。通过对存在强散射体的复杂电磁环境中电磁波的分布特性进行模拟,探讨了抛物方程亚网格技术的高效性。结果表明:与细网格相比,亚网格技术使得抛物方程的计算速度提升了4.57倍,网格空间数下降了86.64%,且较非均匀网格具有更高的计算精度。可见,抛物方程的亚网格模型能够极大地提升抛物方程的仿真效率。     

大气波导中基于抛物方程法的障碍物定位

为了解决遥感遥测、自动导航、电子战等领域中常常涉及到障碍物定位问题,在单向抛物方程法的逆算法的基础上提出了双向抛物方程法的逆算法。应用该逆算法对大气波导环境中的障碍物进行了探测和定位,采用插值法分析了大气波导对障碍物定位精确度的影响。仿真结果表明,通过双向抛物方程法的逆算法可以对传播路径上的障碍物进行探测和定位,而且大气折射率变化会对定位精确度产生较大影响。     

Recursive Two-Way Parabolic Equation Approach for Modeling Terrain Effects in Tropospheric Propagation

The Fourier split-step method is a one-way marching-type algorithm to efficiently solve the parabolic equation for modeling electromagnetic propagation in troposphere. The main drawback of this method is that it characterizes only forward-propagating waves, and neglects backward-propagating waves, which become important especially in the presence of irregular surfaces. Although ground reflecting boundaries are inherently incorporated into the split-step algorithm, irregular surfaces (such as sharp edges) introduce a formidable challenge. In this paper, a recursive two-way split-step algorithm is presented to model both forward and backward propagation in the presence of multiple knife-edges. The algorithm starts marching in the forward direction until the wave reaches a knife-edge. The wave arriving at the knife-edge is partially-reflected by imposing the boundary conditions at the edge, and is propagated in the backward direction by reversing the paraxial direction in the parabolic equation. In other words, the wave is split into two components, and the components travel in their corresponding directions. The reflected wave is added to the forward-wave in each range step to obtain the total wave. The wave-splitting is performed each time a wave is incident on one of the knife-edges. This procedure is repeated until convergence is achieved inside the entire domain.