通信对抗中的电波传播问题

通信对抗对电波传播有关严重的依赖关系。长期以来，重视设备研制而忽视电波传播的研究。无线电侦察和测向受电波特性的影响是多方面的。传播媒介和条件对测向最重要的影响是多波场的扰动。通信干扰同样严重依赖于电波传播。超视距通信对抗的发展依赖于对电波超视距传播特性和规律的进一步认识。     

军用高频通信进展与电波传播研究的关系

文章首先简单回顾了高频通信的发展概况，接着描述用于高频通信的预测程序和为改进高频通信而开展的传播测试研究，最后介绍与高频通信有密切关系的电离层的研究状况。     

近距短波无盲区通信电波传播特性分析

分析近距短波无盲区通信的电波传播方式及性能,对指导工程实践具有重要的意义。在现有研究成果的基础上,总结了陆地地面近距短波通信电波传播仿真计算模型,论述了相关参数的计算取值,针对某在用系统的近距短波通信网,对地波和天波传播进行了Matlab仿真计算及对比分析,得出了较实用的结论。     

电波超视距传播的特点以及在侦察中的应用

本文分析了短波、超短波电波超视距传播的主要技术特点，指出其对通信侦察系统性能的改进和提高的潜在能力并给出传播参数的估计和预测方法。最后考虑了进行超视距、远距离侦察所面对的技术挑战以及系统设计要求。     

电波传播抛物方程模型在航空通信中的应用

针对航空通信中电波传播损耗预测需要满足精确性、实时性及复杂环境适应性的要求,在分析电波传播损耗对航空通信系统作用范围的影响基础上,采用抛物方程模型研究了航空通信中电波在空间区域的传播特性。该模型利用分步傅里叶算法实现快速求解,采用边界平移法处理复杂地形边界,并通过非均匀网格技术提高空间任意一点的场强计算精度,从而改善了复杂环境下电波传播损耗预测的精确性和实时性。将该模型应用于真实地形环境下的航空通信仿真算例中,仿真结果表明：该模型能有效预测复杂环境下电波的传播损耗,评估在正常通信条件下飞行器的飞行范围、最大飞行距离以及最低飞行高度等性能。     

电子浓度具有水平梯度时电波路径的方程

电离层电子浓度具有水平梯度时，可以通过坐标变换，求得曲线的微分方程，而特殊条件下的Ｓｎｅｌｌ定律可以从本微分方程导出，引进小参数λ后可以求解此微分方程。并讨论了λ取各种特殊值的情况，根据各种实际问题定出λ的数值后即可确定电波路径。     

电波传播的文献计量学研究

本文利用文献计量学方法对电波传播的文献规律进行了研究。这些规律包括布拉德福定律、文献老化律和科学生产律（即文献与作者的关系）。文中给出了某些有用的结论。     

基于PETOOL的大气波导环境下舰艇通信电波传播仿真分析

针对面向大气波导环境下的舰艇超视距大容量通信以及通信盲区、通信隐蔽性研究需求,在分析大气波导抛物方程模型的基础上,利用首次同时实现单向和双向抛物方程算法的PETOOL电波传播的天线高度、频率等影响因素进行仿真研究,仿真结果可为设计海上大容量超视距通信系统和科学运用舰艇通信设备提供参考依据。     

城市地形对电波传播的影响研究

随着科技的日新月异,我国通信技术得到飞速的发展,无线电波在人们的工作和生活中发挥越来越重要的作用。怎样提升无线电波的应用质量,是相关部门一直探索的课题。为了掌握无线电波在移动通信中的传播规律以及无线信道的特征,文章进行了城市地形对电波传播影响的试验,测量的对象是距离基站2.5 km处8个不同的测量点,测量目的是研究接收的信号电平状态和规律,并对城市地形对电波传播的影响进行研究。     

隧道内圆极化电磁波传播特性的研究

交通隧道的发展要求实现全程的无线通信。运用波导理论及格林函数法对圆极化电磁波在长直圆形隧道中的场分布及传播特性进行了研究,得到了轴向距离的电场分布计算表达式,与已有隧道内传播损耗模型的比较也表明此模型更准确有效,其结果对于隧道内通信网络的优化有一定的指导意义。     

Mobile and Personal Communications in the 60 GHz Band: A Survey

This paper intends to present a summary of the technical issues arising in the exploitation of the 60 GHz mm-wave band for mobile and personal communications. The most significant applications proposed so far are surveyed, with particular emphasis placed on recent experimentation about millimeter-wave propagation for road/railway transportation as well as indoor scenarios. As a case study, the capacity of a (micro-)cellular Code Division Multiple Access (CDMA) network in the 60-GHz band is also evaluated in detail.     

Verification of background noise in the short wave frequency range according to recommendation ITU-R P.372

The so-called background noise level is a very critical figure in many EMC problems, especially when sensitive radio services are involved. In order to provide a sufficient signal-to-noise ratio (SNR) the minimum signal strength is most commonly calculated on the basis of existing noise levels. On the other hand, if the impact of unwanted emissions on radio services is studied, background noise takes on the function of a reference level. An extensive database of noise levels to be expected is available in the recommendation ITU-R P.372. However, most data concerning man-made noise were already measured in the 1970s. Thus, the significant increase of use of electrical devices with fast digital circuits and various communication systems gives reason to question the validity of the ITU recommendation for today's EMC purposes. This paper deals with different measurement techniques with respect to their suitability for measuring extremely low field strengths in the short wave range and presents measurement results for selected environments. Although the measurements are performed with the constraint of using a mobile measuring setup a considerable sensitivity is reached, leading to the conclusion that the ITU-R P.372 still seems to be valid for estimating noise levels.     

Dynamical properties of rainfall for performance assessment of earth/space communication links at Ku and Ka bands

Knowledge about the dynamic characteristics of rainfall rate and rainfading is of vital importance both for studies on the physical interpretation and modelling of the phenomena and for ancillary studies to counteract rain-induced effects by incorporating some changes in communication system parameters. This paper presents the dynamical characteristics of rainfall observed over Guwahati, India. Using a statistical procedure, an empirical model which predicts characteristic features of rainfading at the Ku and Ka bands is described. The fade inter-event gap statistics as a function of attenuation are discussed for widespread rain and thunderstorms separately. The observed and predicted results are compared with observations made by other investigators. As future communication systems using the Ku and Ka bands are being planned in India and other parts of Southeast Asia (e.g. Measat-I, Thaicom3, AsiaSat3), the results of this study may be used to predict rainfading properties. This study is the first of its kind over India. © 1998 John Wiley & Sons, Ltd.     

用频装备电磁频谱参数泄露风险评估方法

针对通信、雷达等用频装备日益突出的电磁频谱使用安全,以及电磁频谱参数泄露风险量化评估难等问题,本文采用数值、解析等方法对敌我用频装备发射特征、接收敏感特征及天线辐射特性等进行电磁特征参数建模;结合电磁频谱参数泄露完整的通信链路结构,从用频装备效能与电波环境影响角度进行分析,运用网格剖分思想,量化分析用频装备电磁频谱参数泄露概率,提出一种电磁频谱参数泄露概率计算方法,并通过仿真验证了该计算方法。计算得到地面固定雷达L1和1 000跳发射电台M1分别在300~450 km和350~450 km范围内的泄露概率值,实现了电磁频谱参数泄露风险量化评估,解决了电磁频谱参数泄露风险量化评估难问题。     

海上湍流对雷达波传播影响模拟研究

基于海洋大气近地层相似理论,给出了大气折射指数和微波波段湍流强度垂直廓线模型;基于一维Kolmogorov湍流谱,数值模拟随机瞬变大气折射指数,并将其叠加在大气折射率垂直廓线上,建立了海洋大气近地层考虑湍流影响的大气修正折射率垂直廓线模型.利用海面水文气象观测数据和美国海军高级传播模型,数值模拟了蒸发波导和湍流对雷达波传播和雷达探测性能的影响,发现：海洋大气近地层湍流在一定程度上增大了蒸发波导内雷达波传播损耗,减弱了雷达对海面目标的超视距探测能力;而在蒸发波导高度以上部分空域,湍流效应在一定程度上减弱了雷达波传播损耗;因此,在定量评估舰载雷达探测性能时有必要考虑蒸发波导和湍流的综合影响.

     

Submillimeter wave communication versus millimeter wave communication

This paper studies the performance of a submillimeter wave antenna operating between frequencies 0.1 THz and 10 THz with a 4-cyano-4-pentylbiphenyl [5CB] substrate. Since the size and shape of the antenna impact its gain/directivity, resonant frequency, bandwidth, and efficiency, the two antenna types considered in this paper are: (a) Rectangular Patch Antenna (RPA), and (b) Cylindrical Dielectric Resonator Antenna (CDRA). Here a submillimeter wave antenna is compared with a millimeter wave (a few GHz to 100 GHz) antenna. These popular mm-wave antennas are chosen for the submillimeter wave antenna in order to understand changes in their performance as the result of changes in their geometrical shape. FEldberechnung bei Korpern mit beliebiger Oberflache (FEKO) software is used for the design and calculation of the Three-Dimensional (3D) ElectroMagnetic (EM) patterns. This paper also concentrates on the design and analysis of a massive submillimeter wave Multiple-Input Multiple-Output (MIMO) (8 by 8) RPA and CDRA.     

基于三频光外差法产生毫米波的研究

将三频光外差法运用到光纤无线系统(Radio-over-Fiber)中,研究了一种采用三频光外差法产生毫米波的RoF系统.在中心站产生三路不同波长的窄线宽光波,其中两路光波分别由光调制器调制上数据信号,另外一路作为本振光.经光纤传输后,再通过基站光探测器的探测混频产生两个不同频率的毫米波信号.结果表明,采用三束波长为1549.68nm、1549.52nm和1550nm的光波可产生两路分别携带10Gb/s下行基带数字信号的频率为40GHz和60GHz的毫米波,并实现基带信号在单模光纤中 20□的传输.