单站电离层探测系统自动跳频探测模式的设计与实现

结合定频和扫频探测的特点,提出了一种新的探测模式——跳频探测,它可以用于对电离层局部频率精细结构的研究,也可以用于全频段电离层概貌的获取.单站电离层探测系统利用跳频探测模式实现的探测结果表明:在自动跳频探测模式设计中,采用的多线程技术可以很好地实现探测系统硬件控制、数据处理、信息提取与显示、人机交互和自动探测功能,满足探测的实时性要求.同时,采用Matlab引擎技术完成跳频探测数据的处理和显示,使软件获得强大的数据处理和显示能力,并具有开放性,易于升级.     

Diagnostics of the scattering function of a stochastic narrowband shortwave radio channel

The technique for determining the scattering function of stochastic narrowband shortwave channels during ionospheric sounding by linear frequency-modulated signals is presented. The instrumental resolutions of measurements of time delay and Doppler frequency are estimated for a perfect channel. The system developed for determining the scattering function of ionospheric shortwave channels is considered. The results of its investigation with the use of the middle-latitude communications link 5.5 × 10⁶ m long are discussed.     

天波雷达电离层信道可用度统计方法研究

分析了影响天波超视距雷达(OTHR)可用度的电离层信道因素,依据一个太阳活动周期(11年)的电离层不稳定性数据,统计了中纬、中低纬和低纬地区的电离层信道可用度,OTHR频率管理系统综合考虑了电离层的基本特性以及高频干扰频谱分布特性,首次提出了基于频率管理系统工作频率表数据的电离层信道可用度的短期统计方法,并对太阳活动低年特定月份典型时刻(日出、日落、正午和夜间)的电离层信道可用度进行了统计分析.     

基于ITS信道模型的HF信道模拟器的实现

提出了一种基于ITS短波信道模型的HF信道模拟器的实现方法,并给出了线性调频信号通过HF信道模拟器后频域的MATLAB仿真结果。信号通过信道后产生的时延展宽、多普勒频移和多普勒展宽都是利用现场可编程逻辑门阵列来实现。电离层参数是利用三维射线追踪技术根据选定的电离层模型得到。这种HF信道模拟器适用于高达500kHz带宽的信号。利用这种HF信道模拟器,实现了在实验室研究探测信号经过HF信道传输的特性的可能。     

GPS tomography of the ionospheric electron content with acorrelation functional

The authors develop a minimization functional in order to regularize the inverse problem associated with three-dimensional (3D) ionospheric stochastic tomography. This functional is designed to yield, upon minimization, a solution which maximizes the frequency content of the solution below a certain cutoff, while keeping χ² constant. The authors show how this functional can be rewritten in terms of the correlation function of the image, thereby facilitating the algorithmic implementation of the method. They then implement this functional in a Kalman filter and obtain a smoothing algorithm that acts in both space and time. Finally, they use this technique to perform global scale Global Positioning System (GPS) tomography of the ionospheric electron content     

Statistical study of the spectral broadening of skywave signalsbackscattered by the sea surface: application to RMS wave heightmeasurement with a skywave radar

HF skywave signals backscattered by the sea surface are studied on a large set of data (more than 30 h of 64 independent signals) to identify the sources of the broadening of the first-order spectral line. Using high-quality signals reflected by sporadic E ionospheric layers, the natural broadening due to sea-scattering effects has been scaled to about 3/100 Hz. When the signals propagate via F layer, the total broadening due to ionospheric effects is similar in magnitude and can be attributed to two causes. The first, due to frequency modulation effects, which can be identified and corrected, scales on average to 1/100 Hz. The second, called unresolved ionospheric effects, scales on average to 2/100 Hz and is probably due to the spatial variation of the ionospheric Doppler within the ionospheric control volume. Since they are greatly variable with time and space, the influence of these unresolved ionospheric effects can be reduced by sorting spectra, according to the value of the equivalent spectral width, before averaging. Using such sorting and correcting the signals for the ionospheric frequency modulation, 70% of the considered set of data are usable to measure the root mean square (RMS) wave height     

软件无线电在电离层电波探测中的应用

提出了应用软件无线电发展新的电离层电波探测技术，开发新一代电离层电波探测设备的思想，并针对广泛使用的电离层探测设备数字测高仪，详细讨论了软件化数字测高仪的系统结构、特色和可行性。结果表明：发展新的软件化电离层电波探测设备的理论和技术条件均已成熟，它所具有的开放性和灵活性，能更好的满足二十一世纪电离层空间大气研究的需要。     

The effect of ionospheric reflected noise on the performance of anorbital-debris radar system

An orbital-debris radar system was designed to detect the presence of small objects in low Earth orbit by reflecting radio waves off the objects. The author provides a rigorous derivation of the ionospheric reflected noise power and provides an integration over the complete pulse period. Free electrons and ions contained in the ionosphere cause incoherent scatter of the radar signal. This ionospheric reflection tends to increase the noise at the terrestrial radar receiver. A parameter called the ionospheric scattering cross section per unit volume, which is a function of altitude, is useful for computing the power of the ionospheric reflection signal. The Doppler frequency speed of the ionospheric reflected signal is also a function of altitude. The ionospheric noise of a 9-GHz orbital-debris radar receiver is computed using these concepts. Annual and diurnal variations of the noise are included     

基于应答转发的电离层侧向散射传播特性仿真与试验研究

在多模模式下,对侧向散射应答信号的模式特性、频率特性以及群距离特性进行了仿真分析,并与获取的试验数据进行对比分析,验证了基于点到点的电离层侧向散射特性与两条链路上电离层特性关系,即电离层侧向散射的模式是侧向散射两条链路模式的组合,每一个组合模式的最小可用频率与两个模式最小频率的较大值相对应,组合模式的最大可用频率与两个模式最大频率的较小值相对应,每一组合模式的群距离是两种组合模式的群距离的和,为后续电离层特性的研究,以及电离层侧向散射对目标探测、多基地定位、工作参数选择等具有重大的意义.     

利用高频返回散射技术探测电离层行波扰动

 电离层行波扰动(TIDs,Traveling Ionospheric Disturbances)是电离层一种周期性的电子浓度波动结构,它与上层大气内的声重力波运动有关.在前人的工作基础上,提出了利用高频返回散射技术判别TIDs的方法,建立了TIDs特征参数的理论研究方法.并通过分析多方位返回散射试验数据,研究定频返回散射回波信号群距离和跳距随时间、方位角的变化特征,提取了TIDs的运动周期、运动方向、波长等特征参数信息,从而实现对宽空间、大区域电离层波动特性的研究.     

双模电离层闪烁监测系统设计与实现

伴随着北斗卫星导航系统的发展成熟,采用多个卫星导航系统可以获得更多的观测卫星进行电离层闪烁监测,极大提高监测的性能,因此利用GPS系统与北斗系统结合进行电离层闪烁监测成为趋势。文中介绍了所研制的GPS/BD双模电离层闪烁监测系统,它可以实时地监测分析GPS卫星L1/L2频点与北斗卫星B1/B2频点信号的电离层幅度闪烁指数和电离层相位闪烁指数,并可显示和存储各项观测数据。文中对电离层闪烁监测系统的硬件、系统嵌入式软件和电离层闪烁监测上位机软件的设计进行了介绍,对消趋势滤波器的设计和闪烁指数的计算进行了详细的讨论,并在最后给出了系统运行测试结果。     

短波时差定位中电离层参数对定位影响仿真

在短波波段,由于电离层反射传播,电波传播路径与实际地面距离存在较大差异,传统时差定位方法不再适用.文章提出一种基于电离层射线追踪技术的时差定位技术,在此基础上,仿真分析了电离层参数对定位精度的影响.结果表明:在准确获取电离层信息情况下,本方法可准确定位目标;电离层测量误差对定位精度影响较大;站点增加可提高定位精度,降低对电离层参数获取精度要求.仿真结果为短波时差定位系统研制以及电离层参数获取精度要求提供了理论依据.     

A survey of ionospheric effects upon earth-space radio propagation

The frequency dependence is derived and the order of magnitude is presented for various ionospheric effects upon radio waves which have frequencies greater than the penetration frequency of the ionosphere. Among the phenomena considered are phase-path length change, refraction, frequency change, group-path delay, polarization rotation, and absorption. A detailed discussion is given of the mean value and variability of ionospheric absorption, refraction, scintillations, and polarization changes.     

张衡一号卫星观测的地基VLF波电离层加热扰动特征

电离层扰动主要由太阳活动和地球表面活动引起,通过对已知地基甚低频（very low frequency, VLF）波发射源引发的等离子体扰动进行特征研究,对于认识电离层环境变化具有重要的参考意义. 文中主要介绍了张衡一号01卫星原位探测科学载荷等离子体分析仪（plasma analyzer package, PAP）观测系统和数据产出,对该载荷在507 km轨道原位观测的、由地基NWC站大功率VLF人工源辐射引起的电离层加热扰动现象及特征进行了总结和分析. 观测结果表明:氧离子密度、离子温度、离子漂移速度等多个原位观测量在夜侧轨道均同时记录到NWC站上空北侧约50～500 km区域出现的电离层加热扰动现象,扰动持续范围约为300～400 km;通过对相同轨道电场数据进行功率谱计算可知,该区域电场增强主要频率与NWC站发射频率相同. 上述观测结果验证了张衡一号01卫星PAP对电离层离子参量扰动现象具有一定的探测分辨能力,地基大功率VLF电波能够对电离层等离子体环境产生明显的扰动影响,且扰动区域相对于发射源位置向磁赤道方向发生偏移.     

高集成度的高频多普勒探测系统的设计

地震、台风、磁暴等天气事件爆发时,引发的电离层扰动会对无线电波的传播环境造成影响,使空间传播的高频无线电信号产生多普勒频率偏移.针对此问题,提出了一种新型的高集成度的高频多普勒探测系统.通过研发的高集成度的高频多普勒接收机接收来源于电离层反射的高频无线电信号,经过信号处理电路的混频处理获得低中频信号,再通过数据采集卡采集信号并保存在PC机上,利用上位机软件对保存的数据进行实时处理,得到高频多普勒频移的变化曲线,从而研究电离层扰动特征.同时给出了电离层日出效应、偶发E层和行进式电离层扰动等探测实例.实际观测表明:该探测系统运行稳定可靠,可以用于电离层环境的长期监测.     

Ionospheric distortions of high-frequency pseudorandom signals

The ionospheric propagation of shortwave signals with pseudorandom frequency shift are considered with allowance for their coherent and incoherent reception. The frequency ranges within which 1D propagation is realized over ionospheric radio links 2–8 Mm long are investigated, and the dispersion characteristics of these propagation channels are determined. The effect of the dispersion distortions on the reception of pseudorandom signals is investigated, and the maximal permissible signal parameters are estimated.     

电离层色散效应对线极化雷达信号的影响分析

电离层色散导致穿过电离层传播的无线电脉冲信号畸变与失真,严重影响雷达系统对各种地面和空间目标的探测能力.考虑经过电离层传播的线极化雷达信号的相位色散和极化色散效应,参考他人工作推导了具有高斯幅度谱的发射信号与雷达接收信号的卷积包络的表达式,并分析计算了不同频率和相对带宽下接收包络的脉冲宽度和距离分辨率.结果表明:电离层...     

Radio Emission of the High-Latitude Ionosphere as a Result of the Cutoff Mode of the Auroral Ionospheric Duct

Issues of radio emission of the auroral ionosphere are considered with the use of the classical electrodynamics approach, according to which a natural waveguide is formed in the Earth’s ionosphere owing to formation of a trough in the high-latitude ionosphere. Parameters and characteristics of the auroral ionospheric dielectric duct have been estimated on the basis of the obtained experimental data on the properties of the ionospheric trough. The hypothesis that the LF and VLF electromagnetic auroral radio emission in the high-latitude ionosphere is due to the approach of the auroral waveguide to the cutoff mode has been considered. It has been found that the radio emission bands correspond to the eigenmodes of the ionospheric duct under consideration. It has been shown that, within the proposed approach, not only the radio emission frequency band of the high-latitude ionosphere but also the polarization of the radio emission observed in the experiments can be explained.     

Steerable ELF/VLF radiation produced by an array of ionospheric dipoles generated from HF heating

A very low frequency (VLF) or extremely low frequency (ELF) dipole source has been created within the lower ionosphere by modulating the atmospheric dynamo currents with a ground-based high power HF source from the Arecibo Observatory. The authors and their colleagues have demonstrated that ELF or VLF generated in this way and injected into the earth-ionosphere waveguide could be received a few thousand kilometers away. The injection properties due to an array of ionospheric dipoles as a function of array geometry and element currents that will allow steerable ELF/VLF radiation within the earth-ionosphere waveguide are investigated theoretically. The ionospheric array factors for a linear and a planar array of Hertzian dipole sources are developed and their properties examined. The principle of pattern multiplication is then applied to include the effect of the ionospheric array element. This provides a means for predicting the field strengths at a remote receiving site due to a steerable linear or planar array of ionospheric sources generated by high power HF periodic plasma heating.     

高频地波雷达垂直向电离层电子浓度估计方法

高频地波雷达工作时, 往往同时接收到大量的电离层反射回波, 这些电离层杂波会对目标检测造成严重影响, 因此, 电离层杂波抑制是当前高频地波雷达领域的研究热点.文章将电离层回波视为可用信源, 从中反演出垂直方向电离层对应的电子浓度与等离子体频率.对R-D(Range-Doppler)谱图进行预处理, 获取垂直方向的电离层回波谱, 建立其回波功率与电离层雷达散射截面积之间的数学模型, 进而得到对应的电子浓度.在高频地波雷达站进行了实验, 并将反演结果与IRI-2012进行对比, 验证了该方法的可行性和有效性.