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1.
聚焦光束的傅里叶数值算法研究   总被引:2,自引:0,他引:2  
卢光山  胡巍  傅喜泉  喻松  郭弘 《中国激光》2003,30(3):227-230
由于取样定理的限制 ,常规的基于快速傅里叶变换 (FFT)光束传输模拟算法不能进行任意焦距聚焦光束的传输过程的模拟。为此提出了一种新算法 :将球面波因子提出 ,将会聚光束的传输过程转化为非会聚光束的传输 ,从而间接地求得了聚焦光束的光场分布。利用Fresnel数对两种传输过程的关系和聚焦光束的传输特性作了分析  相似文献   

2.
Results from double directional ultrawideband (UWB) channel sounding in a wooden house are described. The double directional channel sounder estimates directional information at both ends of the link, so that we can separate antenna directivity from the channel sounding results. We investigated the dominant propagation mechanisms by introducing cluster analyses. The detected propagation paths from the channel sounding were first classified into clusters in the angular-delay domain, and then properties of the clusters such as standard deviation of path positions, dynamic range of path power, and power distribution of clusters were derived. From the results, we discussed the similarities and differences between the measurement environment and the physical propagation phenomena. Finally, different types of scattering losses of the propagation paths were derived and modeled. The results from sounding and analysis contribute in the development of UWB propagation models and can be used in UWB propagation simulations  相似文献   

3.
In high‐speed wireless communications, an analysis of the propagation characteristics is an important process. Information on the propagation characteristics suitable for each environment significantly helps in the design of mobile communications. This paper presents the analysis results of radio propagation characteristics in outdoor environments for a new mobile wireless system at 781 MHz. To avoid the interference of Korean DTV broadcasting, we measure the channel characteristics in urban, suburban, and rural areas on Jeju Island, Republic of Korea, using a channel sounder and 4×4 antenna. The path loss (PL) measurement results differ from those of existing propagation models by more than 10 dB. To analyze the frequency characteristics for Korean propagation environments, we derive various propagation characteristic parameters: PL, delay spread, angular spread, and K‐factor. Finally, we verify the validity of the measurement results by comparing them with the actual measurement results and 3D ray‐tracing simulation results.  相似文献   

4.
海洋蒸发波导是海上超视距传播的主要机制,对于海上无线电系统的设计和运行具有重要影响.利用在我国南海开展的蒸发波导环境下的C波段微波超视距传播试验数据,对比分析了不同传播距离下的路径损耗和信号快衰落分布特征.试验结果表明:随着传播距离的增大,路径损耗逐渐接近对流层散射传播损耗,主要传播机制也逐渐从蒸发波导传播向对流层散射传播过渡;5 min采样的接收信号电平快衰落分布接近为广义瑞利分布,衰落深度和衰落幅度均小于瑞利分布.所得结果对利用蒸发波导的通信系统设计具有参考价值.  相似文献   

5.
郭淑霞  单雄军  张政  高颖 《激光技术》2015,39(1):124-128
为了解决某些典型场景(如海上、山区、丘陵、城区)下无法使用已有基础模型来全面表达电波传播特性的问题,建立了一种在典型场景下,基于确定性抛物方程、适用于多个传输场景的统一电波传播模型。把典型场景等效为损耗介质层来求解边界条件,利用Fourier分步步进法得到相应解,然后得到电波在典型场景下的传播损耗,并进行了理论分析和实验验证。结果表明,在不同传输场景下,将统一电波传播模型与Miller-Brown模型、射线追踪模型进行比较,结果较吻合,验证了其正确性。这一结果对建立一种求解典型场景下电波传播衰落问题的统一电波传播模型是有帮助的。  相似文献   

6.
7.
This paper is concerned with the determination of the propagation characteristics of modes in the cladded optical fiber which consists of a parabolic-index core and a uniform cladding. The propagation constants of propagating modes are obtained analytically. The results are given in simple form. The asymptotic forms of the propagation constants are also given, which are valid for lower order mode propagation.  相似文献   

8.
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.  相似文献   

9.
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。  相似文献   

10.
Radio propagation at 900 MHz in underground coal mines   总被引:2,自引:0,他引:2  
This paper reports on experimental results of radio propagation in two underground coal mines. Measurements were performed at 900 MHz on horizontal and vertical polarization in typical coal mine operational zones. Values of propagation loss in dB/100 m are derived. Additional losses due to coal mine curvatures and common coal mining equipment obstructions are also presented. A hybrid tunnel propagation model consisting of the free space propagation model and the modified waveguide propagation model is used to explain some measurement results. Based on these results, we believe that microcellular radio communications systems are feasible in coal mines  相似文献   

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