电磁环境仿真中电波传播模型研究及仿真分析

研究了移动通信信道的电波传播损耗模型,通过对不同模型的仿真对比,指出在飞行器控制通信仿真中宜采用Longley-Rice模型的点对点模式,以适应飞行器控制通信的特殊需求。抽取航天飞机雷达地形测绘使命(SRTM)高程数据作为传播模型点对点模式中传播路径的详细地形剖面数据,仿真结果显示电波预测值与理论值吻合度较高。     

近海面电波传播试验与损耗模型分析

介绍了青岛近海海域开展的不同微波波段（L波段、S波段、C波段、X波段）传播试验。给出了不同的海上传播模型,其中包括统计性的Hata模型、Longly-Rice模型以及确定性的抛物方程模型。实测值与模型值比较发现：在L波段,实测损耗数据与Hata模型较为接近,但大部分要大于Hata模型;在S波段,实测数据亦与Hata模型较为接近,但在远距离上,实测损耗数据要小于Hata模型计算值;在C波段,实测数据与确定性蒸发波导传播损耗模型极为一致,Hata模型不再适用;而在X波段,实测数据与标准大气传播模型以及Longly-Rice模型较为接近,但低估了实际传输损耗值,Hata模型亦不再适用。     

电波传播模型的本地化研究

根据目前常用的电波传播模型，研究并提出了对本地化传播模型进行验证评估的方法，使本地化传播模型能更加适合无线电管理工作的需要。     

基于ITU-RP.1546建议书的电波传播仿真研究

本文主要研究了ITU-R P.1546建议书,利用Matlab对该建议书中提出的场强预测方法进行仿真计算,最后结合地理信息数据,举例说明了基于该建议书的监测覆盖分析,进一步说明了该电波传播模型研究可以为VHF/UHF监测站建站规划提供有力的理论依据。     

通信对抗试验外场超短波传播损耗模型修正方法

以移动通信的场强预测方法为基础,提出了一种应用于通信对抗试验外场区的超短波电波传播损耗预测模型的修正方法,根据实际测量数据利用最小二乘法求解模型中参数,实现传播模型的本地化,结果证明修正模型能够达到较高的精度。     

移动通信电波传播场强的数据采集与分析

在当前深入研究移动通信电波传播场强数据采集标准方法的情况下,本文根据移动通信电波传播的理论,通过数理统计分析,详细论述了数据采集中应采用的样本区间长度、样本间隔和重复测量次数,可供实际应用参考。并根据北京市实测数据分别对信号幅度的快衰落概率分布规律和常用传播模式进行了检验,提出了推荐传播模式,有利于降低场强预测中的误差。     

移动通信信道损耗模型研究及仿真分析

针对导弹控制信道特点研究了信道传输损耗模型,提出利用 Longley-Rice模型建立该类通信信道模型,并推导了Longley-Rice模型的具体仿真算法,最后进行了数值仿真分析,实测数据验证了利用Longley-Rice模型建立该类信道的有效性.     

超短波电波传播的分析与计算

以超短波为基础,导出了电波传播的一些计算公式,根据这些公式可对超短波传输的损耗及接收点的场强进行计算。给出了计算实例,具体说明了公式应用方法。分析了超短波传播的几个常见现象,并做出了定性、定量讨论。可供从事超短波通信总体研究及实际设计的人员使用、参考。     

复杂地形中的电波传播损耗预测研究

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。     

A diffuse scattering model for urban propagation prediction

A novel, simple diffuse scattering model based on a ray approach suitable for urban radio propagation is presented. The scattering model is arranged so that the main parameters, having a precise physical meaning, can be easily tuned using measurement results. The model is tested against 900-MHz measurements and the scattering contribution is shown to be important for both received power and channel dispersion in a typical microcellular case     

移动数字电视覆盖预测的射线跟踪模型

中国的几十座城市先后实现了车载移动接收数字电视。当发射天线位置高于城市中的高架桥时,直视区域中桥下道路上的信号覆盖受到桥建筑的影响。为预测毗邻高架桥的地面道路上数字电视信号传播损耗,提出了一种以几何光学理论、几何绕射理论及一致性绕射为基础的三雏射线跟踪模型。综合考虑直射线、地面反射线及桥劈绕射线三种因素,给出计入桥劈绕射的四射线及六射线模型。多径模型计算结果及实测结果表明发收天线间距相同时,覆盖视距区域中毗邻桥梁的地面道路上信号路径增益值因绕射波干涉上下波动;多径射线跟踪模型将有助于移动数字电视的覆盖规划。     

Novel model for propagation loss prediction in tunnels

Radio signal propagation in a tunnel exhibits distinct near and far regions with quite different propagation characteristics. This paper proposes a model that can distinguish these propagation regions and predict their respective propagation losses in the tunnel. The model relies on a break point to separate the propagation regions and a hybrid technique to calculate the propagation losses. The location of the break point is determined with the solution of a novel tunnel-propagation equation for the first time. The solution shows that the location of the break point depends strongly upon frequency, antenna position, and tunnel transversal dimensions. The model is compared with data measured in various tunnels at different frequencies (900 MHz, 1.8 GHz, and 2.448 GHz). The results show reasonable agreement between predictions and measurements.     

Comments on the hybrid model for propagation loss prediction in tunnels

The hybrid model for propagation-loss prediction in tunnels is discussed and its limitations are given. The values from the waveguide model with /spl gamma//sub 2/<2 are applicable for only short distances and for tunnels with low specific attenuation factor (/spl alpha/). In general, /spl gamma//sub 2/ can take any value higher than two.     

非视线单次散射大气传输模型研究

为了研究波长为1.06μm的红外激光散射通信系统各种几何参量对系统性能的影响,利用非视线单次散射大气传输模型分析了接收机、发射机的收发视场、俯仰角以及传输距离等几何参量对接收机接收功率和路径传输损耗的影响。结果表明,增大接收机的视场可以提高探测到的散射光信号功率,而增加发射机的发散角则基本不影响接收到的信号功率;在其它参量不变的情况下,增大接收机或者发射机的仰角都减小了接收机的探测到的信号功率;在散射角和传输距离一定的情况下,适当地降低发射机的仰角可以提高接收机探测到的散射光信号功率。这些结果对系统设计有一定的参考价值。     

ACTS propagation experiment: attenuation distribution observationsand prediction model comparisons

Empirical cumulative distribution functions for satellite-to-ground path attenuation relative to clear-sky values were compiled for 22 path years of data collected by the ACTS propagation experiment. These statistics are for two frequencies, 20.2 and 27.5 GHz, with elevation angles ranging 8-52°, latitudes ranging 28-65°, and five different rain-rate climate regions. The attenuation estimation accuracy was better than 0.3 dB. The availability of the equipment for making measurements was higher than 90% for 18 of 22 path years of observation. The empirical distribution functions were compared with predicted cumulative distribution functions generated by four different attenuation-prediction models: the model recommended by the radiocommunications sector of the International Telecommunications Union (ITU-R); the Dissanayake, Allnutt, and Haidara (DAH) rain-attenuation model; and the Crane-Global and Crane-Two Component models when combined with three different rain-rate distribution prediction models: the ITU-R model the Crane-Global model and the Rice-Holmberg model. On the basis of the expected differences between model predictions and experimental measurements, the only attenuation model that provided acceptable predictions was the DAH model when combined with either the Crane-Global rain-zone model or the Rice-Holmberg rain-race model. A major problem in interpreting the results of the model-versus-measurement comparison is the unmodeled contribution of water on the surface of the ACTS propagation terminal antenna reflector     

A building-transmission model for improved propagation prediction in urban microcells

This paper presents a model for the propagation of radiowaves through buildings. The model can be used as a seamless extension to ray-based propagation prediction models that only consider external reflection and diffraction, as do most current models. This involves the use of so-called transmitted rays, which are traced through building walls. Outdoor-to-indoor propagation (building penetration) is automatically taken into account as a "by-product". The transmission model requires no information about each building's interior other than a specific attenuation factor that describes the global behavior of the field inside the building. This coefficient can be determined for individual buildings by measuring the excess loss associated with the propagation path through the building. It is shown, however, that no large errors are to be expected if all buildings are characterized by the average of the empirical values obtained in this study, at 1.9 GHz. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in accuracy that can be achieved in realistic urban microcell scenarios by taking into account building penetration and transmission.     

ACTS propagation experiment: rain-rate distribution observationsand prediction model comparisons

Empirical distribution functions for one-minute average rain-rate values were compiled for nine station years of observations at five of the Advanced Communications Technology Satellite (ACTS) propagation experiment terminal sites. The empirical distribution functions were compared with cumulative distribution functions generated by three different rain-rate distribution prediction models. On the basis of the expected differences between model predictions and experimental measurements, not one of the model combinations provided good predictions