各向同性电离层低频一跳天波时延特性研究

低频天波的准确预测对于低电离层探测、远程导航授时具有重要意义。该文基于传统“波跳”理论和FDTD方法对地-电离层波导中天波传播时延特性进行研究。结合天地波时域分离技术,给出了100 kHz载频罗兰-C信号在均匀/指数渐变各向同性电离层条件下,距发射台200 km范围内采用两种方法计算的一跳天波时延随收发距离的变化规律。与“波跳”理论相比,该方法可同时考虑地面不规则、电离层昼夜参数分布不均匀的影响,计算精度更高。     

热带丛林地区战术天波通信电路设计综合算图

本文给出一套适用于我国热带丛林地区的战术（１００ｋｍ内）天波通信电路设计综合算图。它可以通过图上作业迅速计算热带丛林环境中天波传播接收场强、发射功率、最低可用频率、电离层吸收．大气天线电噪声场强等。还可以计算丛林叶丛覆盖损耗，丛林中的水平偶极天线的增益损耗，太阳天顶角等。     

基于广义参数化时频变换的天波雷达电离层污染校正

本文引入广义参数化时频变换方法对天波雷达接收信号进行分析，给出了一种更有效和稳健的天波雷达电离层污染估计和校正方法。根据电离层污染的特点选取样条函数作为参数化时频变换的核函数，针对电离层污染后的信号估计核函数参数，利用核函数来估计污染序列，构造污染校正算子进行污染校正。对于多模传播条件下的电离层污染，采用校正后滤除的方式，多次迭代完成污染的校正。仿真验证了方法的有效性和稳健性。      

短波通信频率互易性分析与探讨

文中针对短波通信联络中存在通信频率单向通的问题,首先分析了影响电离层互易性的因素;然后采用ITS仿真软件进行了不同距离和不同方向的双向链路仿真。仿真结果表明同一通信频率在双向链路的传播模式、仰角、电离层反射高度完全一致,并分析了原因;最后在介绍了短波天波链路场强预测方法的基础上分析了系统发射功率、天线、本地噪声等各种影响因素,得出不同条件下短波通信频率互易性的结论。     

利用外部参考源改善OTHR的数据处理

天波超视距雷达(OTHR)由于测量位置分辨率低、电离层瞬时变化引起探测到的目标数据存在不确定性，以及电离层多模引起回波信号的多路径效应，使得相关跟踪处理工作非常困难。该文讨论了OTHR斜坐标转换到大地坐标可能引起的误差，给出了大地坐标系下的基本修正公式。并根据已知外部参考源(如信标、应答机或岛屿等)的回波信号，探讨了一种提高雷达测量值位置配准精度，同时也能有效地消除电离层模式模糊的处理方法。     

无线电监测测向常用名词术语

46电波的跳跃衰落在天波传播过程中,在日出和日落时．由于电离层的形成尚未稳定．由此产生的接收信号的起伏变化。这种现象．在中波和短波每天都在发生。47临界频率（F0）在天波传播过程中．电波由地面垂直进入电离层时,能够被电离层反射回到地面的最高频率F0。也称为零公里最高反射频率。参考频率超过F0时,穿出电离层,不再返回地面。     

短波天波场强数据处理方法研究

针对在短波天波信道中受电离层快衰落影响的场强数据处理问题,提出采用GM（1,1）模型粗大误差判别算法,剔除由电离层快衰落影响而突变的数据,提高数据处理的精度。在Matlab中对短波天波场强典型数据进行处理,利用模糊估计方法计算数据处理前和处理后的瑞利分布,结果表明GM（1,1）粗大误差判别算法能很好地剔除受电离层快衰落影响而突变的数据,具有较好的判别精度,此方法已在装备场强测量中得到应用。     

HF信道的色散带宽及其对脉冲波传播的影响

电离层是时变色散媒质，色散带宽是描述HF信道色散程序的物理量，它安全由电离层的特性决定。文中采用Lin等人给出的色散带宽的定义，将电离层电子浓度进一步推广到球面分层，并给出计算球面分层、各向同性的电离层的色散带宽的普遍关系式。以电离层电子浓度剖面为准抛物层为例求解了色散带宽及其同收发间距和发射频率的关系。计算结果表明当收发间距D＞0且发射频率f＜MUF时，射线分为高角射线和低角射线会发生重合，色散带宽相等。高角射线穿入电离层较深，其色散带宽小于低角射线的色散带宽。提出并通过模拟计算证实了从信号恢复的角度看存在一个最佳的色散带宽，即高、低角射线重合时所对应的色散带宽。     

甚低频对潜通信信号场强预测

甚低频(VLF)电波传播过程中因环境因素影响会使信号产生衰减与扰动,导致潜艇收信可靠性下降.文中基于传播媒质环境地-电离层参数的统计预测,运用波导模式理论对甚低频电波的信号场强进行预测,为甚低频对潜通信系统在运行中调整其可变参数或在特定参数条件下避开传播衰减与扰动提供传播环境服务,使通信系统工作性能与信道特性达到良好匹配,从而实现提高对潜通信效能的目的.     

短波天波传播损耗预测与场强预测分析

简单介绍了短波天波传播在广播通讯中所起的作用,重点阐述了短波天波传播损耗和短波天波场强的预测分析方法,为改善接收效果提供辅助手段。     

Phase of electromagnetic field on the surface of an inhomogeneous earth for sky-wave illumination

A method of calculating the phase of an LF downcoming sky wave in the vicinity of a coastline is presented. The complex integral representation for the resultant field, on the homogeneous earth, is modified to take full account of the inhomogeneity which is in the form of a two-section path. It is shown that there is a phase-recovery effect when the propagation is across the coastline from land toward the sea.     

Comparison of measured and predicted field strengths of medium frequency sky waves over short distances in Japan

Nighttime sky waves of four medium frequencies were observed at distances of not larger than about 300 km in Japan for one to two years of high and low solar activities. The sporadic E (Es) layer always appeared with high probability. Analyzing these data, the following results were obtained: 1) the measured median field strengths are different by at least more than 7 dB from full wave predicted values for the international reference ionosphere (IRI) without the Es-layer. But these agree fairly well with the full wave calculation for IRI with the Es-layer, 2) the field strength approximates the Rayleigh distribution, 3) according to the data for high solar activity, the sky wave appears rapidly after sunset, and during the two to six hours after sunset all median field strengths are about constant.     

应用武汉电离层斜向返回探测系统测量回波相位

电离层作为时空随机变化介质,除了规则变化外还存在着不规则结构和随机变化,即电离层不稳定性,其直接影响是经过电离层传播的电波产生相位随机起伏.利用垂测仪和信标接收机测量精确相位数据的各种方法已被广泛应用,而应用具有大范围电离层探测能力的高频天波超视距雷达测量回波相位的方法还没有文献提出.文中提出了一种从相位编码脉冲压缩体制电离层探测雷达测量的电离层信道双时响应中提取相位数据的理论.此理论被成功地应用于自行研制的武汉电离层斜向返回探测系统中,探测获得了有效的回波相位数据.     

Estimation of the field strength of a low-frequency ionospheric source in the vicinity of the main maximum of distribution on the Earth surface

Simple analytical formulas are derived to estimate the parameters of the main maximum in the surface distribution of the field strength for the low-frequency source located in the Earth ionosphere. The dependences of the relative calculation errors on the source frequency and position are presented. The resulting formulas are applied for loop antennas and for the wave propagation in geomagnetic waveguides (ducts).     

Distribution of the Strength of the Low-Frequency Field Demodulated in the Disturbed Lower Ionosphere over the Earth Surface

The possible distribution of the field strength of the low-frequency demodulated radiation of the high-power transmitter of the HAARP station (Alaska, USA) over the Earth surface in the Earth–ionosphere waveguide has been numerically simulated. It has been shown that, owing to the extremely weak electromagnetic coupling between the ionosphere and the waveguide in the case of an ionospheric source, the strengths of the electric and magnetic fields of the waveguide waves are relatively low and are at the level of the low-frequency noise even in the immediate vicinity of the center of the distribution. It has been confirmed that, in order to detect such a signal and measure its parameters, it is necessary to use special procedures for processing data from ground-based receivers.     

电离层反射区域短波驻波场强的分布研究

精确计算出垂直入射到电离层的HF泵波在整个反射区域的局部电场变化情况对于研究电离层调制实验中产生的各类非线性效应具有十分重要的意义.文章基于泵波垂直入射时一维波动方程和Forsterling方程推导出了特征模式波各电场分量的具体表达式, 并利用“一致近似”的解析法精确计算出线性密度剖面条件下特征模式特征波驻波部分各电场分量和总电场强度在各自反射点附近区域的变化情况.数值计算结果表明:O模式波驻波部分的总电场在其反射点附近区域急剧变化并产生数个极大值, 其幅值增长显著, “电场肿胀”的效应非常明显, 且该效应在高纬地区比在低纬地区更加显著, 地磁场对驻波场强的形态变化具有深远的影响; X模式波驻波部分的电场值在其反射点前虽有一定的增长, 但其增长有限, “电场肿胀”效应远没有O模式波明显.     

The wave propagation and mode coupling in warm ionosphere

The wave propagation in warm ionosphere is studied in both homogeneous and inhomogeneous ionosphere. When the temperature of electrons are taken into account, the plasma wave is a propagating wave. The dispersion relation of waves in warm ionosphere has been derived. It is an algebric equation which is analogue to the Appleton-Hartree equation, but in higher order. In a stratified warm ionosphere, the equation forq (Booker’sq) is an algebric equation. Both of these equations are used in study of the wave propagation in the ionosphere by means of ray tracing method. The wave mode linking in homogeneous ionosphere and mode coupling in stratified ionosphere are studied. The mode coupling between plasma wave and electromagnetic wave is discussed through the discussion of singularity of the wave equation. The wave fiold near the wave transformation region can be found out by solving the wave equation near the singularity. The justification of study mode conversion by ray tracing is explained. The results could be useful in the study of wavo absorption process and radio heating experiments in the ionospheres.     

基于二维解析射线追踪的短波电离层轨迹研究

考虑短波在电离层中通过单F层反射传播的情况,结合一种特定电离层电子浓度分布(准抛物)模型,利用二维解析射线追踪技术得到短波轨迹中参数的解析表达式.在此基础上分别对射线在频率固定、仰角变化及仰角固定、频率变化两种情况下的轨迹进行了讨论,得出频率和仰角对短波传输的地面距离及群路径的关系.最后对不同因子对轨迹的影响及短波轨迹进行了仿真.仿真结果表明,该方法在研究短波电离层传播轨迹中有很好的应用价值.     

The ground field of arbitrarily shaped linear antennas ofgeostationary satellites in polar regions taking into account astochastic and anisotropic ionosphere

The propagation of electromagnetic waves from satellites to the earth is influenced by the electrically anisotropic behavior of the ionosphere. Fluctuating ionospheric parameters cause perturbations in the signal. To calculate the ground field of arbitrarily shaped linear antennas of geostationary satellites for polar regions, the passage of a carrier wave through a homogeneous, electrically anisotropic, stochastic ionosphere imbedded in a two-dimensional three-layer model (near-earth space, ionosphere, atmosphere) is considered. Perturbations due to the ionospheric fluctuations are treated using B.J. Uscinski's multiple scatter theory (see The Elements of Wave Propagation in Random Media, McGraw Hill, 1977) which has been extended to anisotropic media. Finally, the theory of E. Arbel and L.B. Felsen (see Electromagnetic Theory and Antennas Part I, Pergamon, 1963, p.391-420) is applied to derive field representations for the more realistic case of a homogeneously stratified anisotropic ionosphere