共查询到20条相似文献,搜索用时 203 毫秒
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远距离不规则复杂地形中,电波传播损耗计算精度较低,对此,文中提出了一种基于地理信息系统并根据实际地形提高电波传播损耗计算精度的算法模型,构建了可视化的软件显示平台。首先,根据国际电信联盟(ITU-R)的P系列电波传播建议书,结合实际地理信息情况获取了地形和环境因子的数据。然后,通过数字地图模型,针对传播路径上各种不同地形区域,分别建立传播模型来计算电波传播损耗,并完成仿真计算界面的设计和实现。最后,给定收发天线高度和频率,依据实际地形,建立完整的电波传播模型进行仿真实验。结果表明,该算法模型不仅能得到传播路径上每一个点的损耗,而且与传统的Hata模型对比,该算法在不同区域和地形中敏感度更高,可以有效提升传播损耗计算精度,更适用于计算实际地形中远距离不规则复杂地形下的电波传播损耗,帮助改善通信质量。 相似文献
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Ming-Shing Lin Ruey-Beei Wu Chun Hsiung Chen 《Antennas and Propagation, IEEE Transactions on》1993,41(10):1456-1459
An equivalent-transmission-line-circuit (ETLC) model is developed to discuss the transient propagation problem of a plane wave in inhomogeneous, anisotropic, and transversely lossy slabs. This model is based on the analogy between the field equations and the coupled transmission line equations. By establishing the analogy, suitable lumped-circuit models are proposed to treat the equivalent transmission lines, which may then be solved by the circuit simulation program. In this study, the accuracy and convergence of the lumped-circuit models are examined. The ETLC model is then applied to discuss the propagation problem in anisotropic graphite/epoxy laminates with numerical results presented to show the transient responses due to the electromagnetic pulse and Gaussian pulse 相似文献
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In this paper, the behavior of wave propagation through coniferous forest stands at millimeter-wave frequencies is characterized both theoretically and experimentally. A coherent wave propagation model is used to simulate the propagation through foliage. The coherent model is composed of two components: a forest stand generator that makes use of a stochastic fractal model, and an electromagnetic model that makes use of Foldy's approximation and single scattering. An outdoor measurement system is designed and used for characterizing the channel behavior for a pine tree stand at Ka-band (35 GHz). In this experiment, 84 independent spatial samples of transmitted signal through the pine stand were collected to obtain the path-loss statistics. The comparison between measurement and simulation results showed that single scattering theory overestimates the wave attenuation through foliage. To improve the accuracy of the coherent model, partial multiple scattering occurred among the needles of highly dense leaf clusters must be included for the estimation of the coherent attenuation. Distorted Born approximation is used to macromodel the scattering pattern from needle clusters. This technique has comparable accuracy and requires much less computational resources than a full-wave solution, such as method of moment. By including multiple scattering effects of needle clusters in the simulation model, much better agreement is obtained for both mean and standard deviation of the path-loss. 相似文献
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首先介绍无线电波的传播特性以及传播模型的分类;然后对Crosswave射线追踪模型进行详细分析;最后结合某区域的TD-LTE网络规划仿真案例,论证Crosswave射线追踪模型在TD-LTE网络规划中的可行性和准确性。 相似文献
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为探讨有限元方法研究超声横波检测问题的可行性与有效性,设计了斜探头检测带横孔试块的计算模型,利用Ansys软件使用二维平面应变模型进行了有限元计算。作为对照,利用声线法计算了声波的传播路径及波型转换情况,利用光弹试验观测了声波与横孔的相互作用。计算与分析结果表明,有限元计算结果可揭示出声波的传播规律,可观测到声波在界面上的反射、折射规律,可将声波与缺陷相互作用的前后过程可视化显示;超声横波检测的有限元模拟计算结果与声线法、光弹试验的结果,具有良好的吻合性。 相似文献
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Hsu-Feng Chou Ching-Fuh Lin Gin-Chung Wang 《Lightwave Technology, Journal of》1998,16(9):1686-1693
An iterative finite difference beam propagation method based on the Crank-Nicholson scheme is presented to simulate continuous wave (CW) second-order nonlinear effects in optical waveguides with the depletion of the pump wave taken into account. This method is an extension of the linear finite difference beam propagation method and preserves the same order of accuracy. Comparisons with the previously published explicit finite difference beam propagation method and the rectangular approximation method are presented. Quasi-phase matched difference frequency generation in AlGaAs and quasi-phase-matched second harmonic generation in LiNbO3 are considered in the evaluation, showing that one iteration for the IFD-BPM is sufficient for the simulation with good accuracy and without increasing much computation time 相似文献
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Yunxing Ye Pranay Swar Kaveh Pahlavan Kaveh Ghaboosi 《International Journal of Wireless Information Networks》2012,19(3):229-238
In this paper, we derive and analyze cooperative localization bounds for endoscopic wireless capsule as it passes through the human gastrointestinal (GI) tract. We derive the Cramer-Rao bound (CRB) variance limits on location estimators which use measured received signal strength (RSS). Using a three-dimension human body model from a full wave simulation software and log-normal models for RSS propagation from implant organs to body surface, we calculate bounds on location estimators in three digestive organs: stomach, small intestine and large intestine. We provide analysis of the factors affecting localization accuracy, including various organ environments, external sensor array topology, number of pills in cooperation and the random variations in transmit power of sensor nodes. We also do localization accuracy analysis for the case when transmit power of the sensor is random with known priori distribution. The simulation results show that the number of receiver sensors on body surface has more influence on the accuracy of localization than the number of pills in cooperation inside the GI tract, The large intestine is affected the most with the transmit power randomness. 相似文献
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该文基于ABAQUS有限元软件建立了压电陶瓷材料与混凝土的机 电多物理场耦合数值分析模型,对压电波动法检测混凝土裂缝和弹性模量测定进行数值模拟,探究其损伤识别的机理。采用C3D8E压电单元模拟压电陶瓷(PZT),采用C3D8R单元模拟混凝土梁,采用三维时域粘弹性人工边界消除边界对应力波的反射。模拟结果表明,嵌入式PZT片激发的应力波包括纵波和剪切波,其中剪切波的幅值比纵波大,传播速度比纵波慢。以信号相对能量(Di)作为损伤程度判别因子,其值随着裂缝的深度增加而降低。将数值模拟计算的Di和混凝土的动弹性模量(Ed)与试验结果进行对比,符合较好,说明有限元方法可以有效地解决该类问题。 相似文献
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结合地理信息技术(Geographic Information Sciences,GIS)的计算机仿真,已经成为无线电传播信道分析的重要手段之一。仿真软件“移动无线电”(Radio Mobile)可以对指定地形下的无线电波传播过程进行数值模拟,直接识别并导入多种地形数据,但并不包括当今精度最高且国内广为流行的免费地形数据——先进星载热发射和反射辐射仪全球数字高程模型(Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model,ASTER GDEM),其精度可达30 m。因此,介绍一种如何将ASTER GDEM的数据读入Radio Mobile的处理方法。首先,利用GIS软件Global Mapper将ASTER GDEM压缩包数据转换为按照经纬度排列的DTED数据;其次,将DTED数据整理到以经度命名的文件夹内,每个文件按照纬度命名;最后,在Radio Mapper的地图属性设置中输入待仿真地域的经纬度,完成地形数据的导入。在此基础上,针对某一指定经纬度导入地形场景,利用Radio Mobile对电磁波的路径损耗做了初步的数值仿真。 相似文献
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The application of the finite-difference time-domain (FDTD) technique to problems in ionospheric radio wave propagation is complicated by the dispersive nature of the ionospheric plasma. In the time domain, the electric displacement is the convolution of the dielectric tensor with the electric field, and thus requires information from the entire signal history. It is shown that this difficulty can be avoided by returning to the dynamical equations from which the dielectric tensor is derived. By integrating these differential equations simultaneously with the Maxwell equations, temporal dispersion is fully incorporated. An FDTD approach utilizing the vector wave equation is also presented. The accuracy of the method is shown by comparison for a special case for which an analytic solution is available. The method is demonstrated with examples of pulse propagation in one and two dimensions. The computational limitations of present-generation computers are discussed. The application of this approach to the study of wave propagation in randomly structured ionization is addressed 相似文献
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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。 相似文献
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为了直观地显示超声波脉冲在固-固界面的传播规律,建立了两种玻璃组成的固-固界面有限元模型,模拟了超声波脉冲在固-固界面的传播情况。通过不同时刻的波场快照图,清晰地显示出超声波脉冲在不同声学参数的两种固-固界面的传播情况,模拟得到的结果与理论和实验结果相符。模拟结果表明,通过有限元模拟方法正确的模拟了超声波脉冲在固-固界面中的传播过程,清晰地观察到了在界面上形成的复杂声场情况,模拟结果可为超声无损检测技术在检测参数选择、缺陷特征提取等方面提供一定的参考。 相似文献
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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. 相似文献