东亚地区夏季Es的分布特性

东亚地区是全球Es出现的峰值区域.以往关于东亚异常的研究和讨论具有一定的局限性, 或者由于缺乏中国区域的资料而论据不足, 或者缺乏中国、日本Es中心的详细对比.文中利用中国及周边地区23个垂测站二十余年的Es数据进行空间插值分析, 给出东亚地区夏季Es出现率的空间分布等值线, 并深入分析东亚异常中心区域的时间变化特征.研究表明, 中国重庆、广州或者日本山川、国分寺、秋田是夏季Es的高发区域, 东亚异常中心始终位于其中某个地区, 具体位置随着统计指标改变; 高发区域内的Es强度呈现出年变化和日变化, 中国高发区域Es强度的昼夜差别比日本高发区域更为显著, 但后者具有更为复杂的年变化和昼夜变化特征, 这对揭示中纬Es形成原因具有一定的意义.     

青岛地区电离层Es特征统计分析

利用青岛电波环境观测站电离层测高仪2001年至2011年共11年的观测数据,对Es层的季节变化和日变化特征进行了统计分析.统计结果表明:Es层发生概率与临频的季节变化和日变化为单峰结构,夏季和中午是Es发生最频繁和最强的时间;虚高的季节变化和日变化为双峰结构,季节上以4月份和9月份为主次峰,日变化上以7点和17点为主次峰;Es类型的发生次数从高到低依次为平型、低型、高型和尖型.     

中国南部地区Es层出现规律统计及分析

利用中国地区广州和海口两个常规观测站一个太阳周的历史数据(1996～2006年),根据突发E层(Es层)临界频率的不同取值范围对我国南部地区Es的出现概率和临界频率的变化规律进行了统计与理论分析.统计结果显示,中国地区是Es高发区,对于各种强度的Es层都是在夏季白天时段出现概率最大,最大可以达到90%以上;此外,Es层临界频率具有与F2层临界频率类似的变化规律,在正午时刻前后达到最大值,但Es层出现概率与太阳活动性没有绝对的依存关系.可见,Es层对夏季高频通信影响很大,白天时段受影响程度更大.     

2020年6月21日日环食电离层Es响应研究

为研究日环食期间电离层Es演化过程,利用VHF相干散射雷达和便携式垂测仪在2020年6月21日日环食期间开展联合观测试验,得到日环食期间h′Es和f_oEs均呈现出先降低再增强的变化形态.分析表明,该演化过程类似于快速日出日落对电离层Es的影响,其成因是日环食期间太阳活动作为辐射源经历了快速减弱、复原的一个过程.本次试验观测结果对研究和完善电离层Es形成机制、机理有重要意义.     

典型环境下短波通信场强计算建模研究

综合分析短波地波、天波传播机制,依据短波通信典型环境,研究实际情况下短波通信场强模型的建立方法。     

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。     

短波天波传输中接收端场强估算方法

天波传播是短波信号传播的方式之一,不同条件下其通信范围跨度较大。本文基于国际电信联盟相关研究成果,介绍了近、中、远三种短波天波传输距离情况下的路径场景、传输中的电波损耗及进行接收端场强估算的方法,为短波通信系统通信频率选择提供参考。     

短波发射机覆盖场强的测试研究

这篇文章主要针对功率较小的（5KW以下）短波发射机为例子,检测机器在单频工作方式下频率跟场强的联系、天线阵子夹角与跟强的联系,研究短波发射机覆盖场强,并归纳出短波发射机周边覆盖场强跟电磁环境都可以应用的结论。     

中、短波广播场强测量应注意的问题

本文在简介场强测量原理基础上,总结性地介绍了中、短波广播场强测量如何选择测量设备和测量场地,对不同测量项目内容采取不同测量方法及技巧,电场强度单位的正确应用和换算,场强中值的统计方法等.     

A simplified HF field strength prediction procedure for India

Field strength measurements of several HF broadcast transmissions were made at New Delhi during 1987-1990 with a view to evolving a simple procedure for estimation of the skywave field strength in the HF bands (3-30 MHz). An attempt has been made using the measured field strength values to arrive at a single combined loss factor which can account for all the losses in excess of basic free space and ionospheric absorption losses. The present study has shown that a provision of 4 dB for transmission losses other than free space and ionospheric absorption losses can bring the predicted values closer to measured field strength values for single-hop circuits in India for about 50% of the cases, and 10 dB increases it to 90%. Transmission losses in general were found to be much higher during equinoctial months in India, particularly around the peak region of equatorial anomaly     

连续波HF化学激光器计算浓度场的简化模型

介绍一个计算连续波HF化学激光器浓度场的简化模型。假设速度场与普通平板边界层速度场相似。温度场与浓度场是用联立能量与组份守恒方程以及相似的速度场求解得到的。求得了混合、化学反应区的界面曲线,并研究了气流速度、温度以及化学反应等对激发态HF浓度的影响。     

An improved HF field strength prediction method

A multi-correlation process for reducing the RMS error between the field strength values predicted by the use of the method laid down in Report 894.2 (1991) and the values of Databank.D1 is described. Three functions are used. The first function has 1080 coefficients describing 10 distance ranges, 4 solar activity ranges, and 27 frequency to MUF ratio ranges. The second function covers 10 distance ranges and 24 local time data in the mid path with a total of 240 coefficients. The third function has 720 coefficients covering 10 distance ranges, 6 modified dip angle values, and 12 months. With the use of these functions, the final RMS error is 7.69 dB for the whole set of circuits of Databank.D1 database and 7.29 dB for short paths. The Report 894.2 method has a RMS error of 10.1 dB. Four plots are included to compare that method with the improved method     

A study of HF field strength variation in India and its prediction

Measured field strength data pertaining to several HF broadcast transmissions monitored in India during 1987-90 has been analysed to study solar activity, local time and seasonal variations in the field-strength. Values tend to saturate at high solar activity levels when sunspot numbers are beyond 120. Variations in field strength have also been studied with varying ratios of operational frequency to maximum usable frequency (f_op/MUF) and equivalent vertical frequency of the links. Based on this study a prediction method for HF field strength has been suggested for India. Comparison of values estimated using this technique has been made with actual measured field strength values for different HF transmissions for different months. This method is to be particularly suitable for field operators     

计算电大尺寸建筑物内电波场强的PSTD方法

本文采用一种新的时域数值方法－伪谱时域（ＰＳＴＤ）法来计算电大尺寸建筑物内电波场强。提出了由初始条件技术和一维ＰＳＴＤ方程对入射平面波脉冲进行模拟,并利用纯散射场法和线性插值把平面波引入求解问题空间,有效地解决了ＰＳＴＤ方法中入射波设置问题。数值结果表明这种新方法用于模拟电大尺寸建筑物内电波场强的精度和有效性。     

两种新的抑制高频雷达中Es层干扰的自适应算法

提出了两种新的抑制Es层杂波的自适应对消算法,分别是频域瞬时值LMS算法和归一化频域瞬时值LMS算法。频域瞬时值LMS算法是利用辅助天线输出的Es层杂波瞬时值来估计主天线当前输出中的Es层杂波成分,可以更大程度上抑制Es层杂波。而归一化频域瞬时值LMS算法则是在频域瞬时值LMS算法的基础上增加归一化的过程,可以大大缩短自适应过程的收敛时间。     

My memory of efforts in developing CCIR Recommendation 534-3:method for calculating sporadic-E field strength

Study Group 6 of the ITU Radio Communication Sector (ITU-R, formerly CCIR) deals with ionospheric propagation. The Study Group has twelve Recommendations, among which those recommending methods for calculating and predicting radio-signal strengths are the ones that telecommunications service providers need most. Rec. 534-3, concerning the method for calculating sporadic-E field strength, is one such Recommendation. Radio-wave propagation via the sporadic-E layer (Es) was expected, during the “short-wave age”, to be a possible communications medium. But today, it is treated as a potential source of interference with television signals, because of its irregular behavior. The progress in studies of Es propagation characteristics, and the existence of data banks of f₀Es data (f₀Es is the critical frequency of the ordinary wave in vertical-incidence radio sounding), obtained through worldwide observations, made it possible to construct a prediction method with worldwide applicability. The author describes the birth of the Recommendation, and the efforts made towards its realization     

Analytic models for calculating the rain brightness temperature in the millimeter and centimeter wave bands

Three analytic models for calculating rain brightness temperature T _br in the millimeter and centimeter wave bands are proposed. The choice of the radiation model required to calculate T _br of the system formed by the atmosphere in the presence of precipitation and by the Earth’s surface is validated on the basis of the analysis of various physical processes affecting this radiation. These processes include absorption and scattering of radiation by hydrometeors as well as self-radiation and reflection from the Earth’s surface.     

一种采用多分辨率设计的短波信号分析方法

由于短波频段信号种类众多、特征各不相同、参数各有变化,时变非恒参信道对信号侦察产生较大影响,因此短波信号分析面临有一定难度的问题。基于这一实际问题,提出了多分辨率分析方法,即对不同信号采用适合信号特点的分辨率下进行信号分析,对采集外界的短波2FSK、8FSK、多音并行PSK及话音等信号在多种分辨率下的信号特征呈现进行了比较,得到了每个信号的最佳分辨率,仿真结果表明,每种信号适用于信号分析的最佳分辨率各不相同,而且与信号特征参数密切相关。     

A model for calculating the radiation field of microstrip antennas

Starting from the equivalence principle, an aperture model is developed for calculating the radiation field of microstrip antennas. In this communication the model is applied to the rectangular microstrip resonator antenna. Antenna characteristics, like patterns and radiation resistance, are computed and compared with experimental results. The model and the calculations include the higher order modes as well as the fundamental mode of the resonator antenna.