复杂环境下电波传播损耗的测试与仿真

确定性的电波传播特性预测方法为通信装备内场仿真测试中所需的通信链路传播损耗计算提供了一条高效准确的途径。采用外场实地测试和基于射线追踪算法的确定性电波传播损耗预测软件,仿真2种手段对真实环境下某条特定通信链路的传播损耗进行了预测,给出了测试和仿真结果,分析了误差来源,表明了采用基于射线追踪算法的确定性电波传播损耗预测方法对复杂环境下通信链路传播损耗计算的可行性。     

800 MHz mobile radio propagation prediction using Kalman filteringtechniques

A method is presented to derive a propagation model to predict the received median signal voltage for an 800-MHz mobile radio system. Results are given of an investigation into the performance of a particular model that was derived using this method. The method uses a Kalman filter that uses propagation measurements to derive a best fit for a particular propagation model to the measured data. The model that was derived is based on propagation measurements made in the State of Florida. The new propagation model uses a plane-Earth propagation model that is corrected with an environmental propagation loss term that takes into account the various environmental effects near the mobile unit. The parameters in the environmental propagation loss model were determined using a Kalman filter that computes minimum mean square estimates of the parameters using measured propagation data. The environmental propagation loss term accounts for the effects of Earth diffraction, hills, valleys, urban and suburban areas, bare and grass-covered ground, bushes, trees, swamps, and propagation over fresh and salt water. It was found that, with the 800-MHz propagation model derived with this method, the prediction error for the received median signal voltage had a standard deviation of 5.08 dB     

On-body propagation loss estimation using method of equivalent sources

A new method for the fast estimation of the on-body propagation loss is proposed. The method is applicable for a variety of propagation models but limited by a far-field zone observation point. The technique is based on the equivalent source theorem. Knowing the propagation losses for an infinitesimal current source, propagation losses of real antennas can be obtained with only the knowledge of their equivalent currents over a surface surrounding the antenna. The method can be applied for any kind of excitation signals and offers reduction in simulation time. It has been verified using both monochromatic and Gaussian pulse excitation and good agreement is obtained compared with a full conventional FDTD model with a simple antenna.     

随机波束研究超宽带室内多径信道特性

从随机桥过程出发引入随机波束概念,使用随机波束研究超宽带（UWB）室内多径信道的传播特性.将UWB信号多径传播轨迹视作随机过程的样本,得到建模多径信道传播特性的随机波束.使用随机波束构建UWB信道的多径传播模型,并给出使用随机波束方法分析UWB室内多径信道特性的算法.使用该信道模型对实际传播环境进行仿真分析,并与其它建模UWB多径信道的方法进行了比较.仿真得到的UWB信道的功率延迟分布特性与实验测量的结果非常一致,证明此方法的有效性.     

Three-dimensional finite difference beam propagation algorithms forphotonic devices

Finite difference beam propagation techniques are developed for photonic devices with step-index distributions and arbitrarily large index differences. One technique, the eigenvector expansion method allows large propagation steps along uniform waveguide sections. The second technique, a propagation matrix series expansion method, is particularly suitable for three-dimensional wave propagation simulations. It can easily handle 10⁵ discretization points on personal computers or workstations. The first method employs absorbing boundary conditions while the second utilizes transparent boundary conditions at the edges of the computational windows. The accuracy and applicability of these techniques is demonstrated for several 2-D and 3-D test structures     

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...     

Propagation of double-exponential pulse through Debye medium

The saddle point method is applied to the problem of signal propagation through Debye medium. The steepest descent method is used to calculate the propagation of a double-exponential pulse through Debye medium, and the results are compared with those obtained through Hosono's (1980) method and finite-difference time-domain (FDTD) method. It is found that a Gaussian function can be used to approximate the propagated signal for sufficiently long propagation distance and the analytical representations for the amplitude, center, and width of the propagated pulse are obtained based on the first-order asymptotic representation. An analytical approximation of the saddle points valid for late time is also obtained     

Propagation of elastic waves in phononic crystals

Propagation of elastic waves in a system of cylindrical channels embedded in a homogeneous isotropic elastic medium (a phononic crystal) is investigated. A multipole method is proposed for simulation of wave propagation in such structures. The dispersion characteristics of wave propagation in systems consisting of three, six, and seven cylindrical channels are calculated. The results are compared to the data corresponding to wave propagation along a single channel. The computational efficiency of the method and its applicability to simulation of the propagation of elastic waves in large phononic crystals are assessed.     

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.     

Approximate scalar finite-element beam-propagation method withperfectly matched layers for anisotropic optical waveguides

The perfectly matched layer boundary condition for arbitrary anisotropic media is incorporated into the approximate scalar beam propagation method. The procedure is based on a finite-element method for three-dimensional anisotropic optical waveguides with off-diagonal elements in a permittivity tensor. In order to treat a wide-angle beam propagation, the Pade approximant operator is employed. To show the validity and usefulness of this approach, numerical results are presented for Gaussian beam propagation in free space and Gaussian beam excitation on a three-dimensional anisotropic optical waveguide     

超视距低空电波传播模式研究分析

文中提出了一种电波传播模式分析方法. 通过对PJ (Paulus-Jeske)波导进行参数估计,实现蒸发波导的完备性建模;采用抛物方程法分析气象环境中的二维电波传播路径损耗分布,利用最大值池化降低数据量,并采用自适应聚类分析实现电波传播模式分析,进而建立海杂波衰减规律与电波传播模式之间的映射,统计条件概率. 结果表明,蒸发波导环境下海杂波衰减与电波传播模式之间具有相关性,分析结果能够展示蒸发波导中的电波传播模式,并且能够为海杂波反演大气波导提供先验条件概率分析.     

The semivectorial beam propagation method

Details of an efficient semivectorial beam propagation method are presented. The propagation is determined by solving the finite-difference equation in alternating directions. Unlike the traditional split-operator beam propagation method, in the semivectorial method the index term is not separated from the spatial differentiations. Since boundary conditions at dielectric interfaces can be satisfied by two orthogonal polarizations individually, the method is semivectorial. The performance can be enhanced by using a nonuniform grid. By modifying the routine, it can also be applied to periodic structures. Numerical results for rib waveguides are presented     

阵列波导光栅中自由传播区模式的有效折射率

针对阵列波导光栅设计中自由传播区模式有效折射率的确定问题,提出了一种采用加权等效模式折射率作为自由传播区模式有效折射率的方法。通过引入慢变包络近似条件并采用吸收边界条件的一阶Galerkin有限元法,给出了阵列波导光栅自由传播区仅含有磁场分量的全矢量波动方程组。在此基础上,基于三维全矢量束传播法对自由传播区光场进行了模式分析,并结合导模传输分析法,推导给出了加权等效模式折射率的表达式,为阵列波导光栅设计中自由传播区模式折射率的确定提供了一个理论依据。     

An Efficient Bidirectional Propagation Method Based on Dirichlet-to-Neumann Maps

A new bidirectional propagation method is developed for numerical simulation of waveguiding structures with multiple longitudinal discontinuities. It is a noniterative method based on the Dirichlet-to-Neumann map of each uniform segment. The method is more accurate than existing bidirectional beam propagation methods and it does not require the computation of eigenmodes in each segment.     

A new iterative bidirectional beam propagation method

A new bidirectional beam propagation method is developed for numerical simulation of wave-guiding structures with multiple longitudinal reflecting interfaces. It is an iterative method that works on the wave field components directly. Operator rational approximations developed in the one-way beam propagation method are used together with a modern Krylov subspace iterative method. Compared with earlier bidirectional beam propagation methods based on the transfer matrix formulation, the new method is numerically stable and models evanescent modes better     

Finite element beam propagation method for three-dimensionaloptical waveguide structures

A beam propagation method (BPM) based on the finite element method (FEM) is described for longitudinally varying three-dimensional (3-D) optical waveguides. In order to avoid nonphysical reflections from the computational window edges, the transparent boundary condition is introduced. The present algorithm using the Pade approximation is, to our knowledge, the first wide-angle finite element beam propagation method for 3-D waveguide structures. To show the validity and usefulness of this approach, numerical results are shown for Gaussian-beam excitation of a straight rib waveguide and guided-mode propagation in a Y-branching rib waveguide     

Wide-Angle Alternating-Direction Implicit Finite-Difference Beam Propagation Method

An alternating direction implicit (ADI), scheme for the wide-angle finite-difference beam propagation method (FD-BPM) based on the wide angled Pade multistep method is presented. The scheme incorporates an iterative technique for correction of the operator splitting error. The resulting equations are efficiently solved by the Thomas algorithm for tri-diagonal band matrices. The dispersion characteristics, accuracy and stability of the scheme is verified analytically and numerically for the cases of a plane wave propagating at fixed angle to the assumed propagation direction of the algorithm and the three dimensional angled propagation of a Gaussian beam. The computational requirements of the method are assessed against a standard wide-angle Pade multistep method that uses direct and iterative sparse matrix solvers.      

Efficient and accurate vector mode calculations by beam propagationmethod

An in-depth study of the beam propagation method for the vector mode calculation of optical waveguides is presented. It is established that the imaginary-distance propagation method may be generalized to vectorial modes for arbitrary structures by combining it with the finite-difference vector beam propagation method (FD-VBPM). A simple, unified theory and analysis are developed. An assessment of the accuracy and efficiency is carried out by comparing the simulated results with the analytical solutions for well-known structures     

A Novel Approach of Modeling Cladding-Pumped Highly Er–Yb Co-Doped Fiber Amplifiers

We present a new modeling method for cladding-pumped highly Er-Yb co-doped fiber amplifiers. The method combines the beam propagation method (BPM) for the field propagation and nonlinear rate equations for the laser medium. The pump absorption, which is obtained numerically from the nonlinear rate equations, is used in BPM calculations of the field propagation. As a result, our method can effectively deal with difficult issues such as the multimode nature of cladding pumped schemes even in complicated structures, as well as strong nonlinearities in highly Er-Yb-doped fiber amplifiers. The simulation results are in very good agreement with experiments having different structures and different concentrations of Er-Yb. The method is particularly well suited to active fibers with low amplified spontaneous emission power, but it can also be developed further for more general cases.     

基于抛物方程的海上电波传播研究

抛物方程已经被广泛地应用于电波传播预测模型,并成为解决电磁波传播问题的主要工具。针对目前大多数预测模型处理粗糙海面的不足,引进了一种能包含海面阴影效应的粗糙度修正因子,并由于电波在海面上传播主要受到蒸发波导和粗糙海面的影响,结合抛物方程和蒸发波导理论对海面上的电波传播进行了研究,利用PE模型计算了电波在蒸发波导中不同条件下的传播损耗,并分析了蒸发波导和粗糙海面对电波传播的影响。