利用单站电离层测高仪与GPS数据的同化反演试验

利用测高仪和GPS观测数据进行了单站电离层电子密度廓线的同化反演实验,实验中设计了一套基于Kalman滤波的电离层数据同化系统,采用了水平和垂直方向可分离的高斯型误差协方差矩阵,利用IRI2000模式作为同化反演的背景场,分别使用了测高仪数据和GPS数据进行了单独同化反演和联合同化反演实验,结果显示：在各类同化参数不改变的情况下,单独利用GPS数据反演结果较好,不仅可以得到较为准确的TEC,电子密度廓线结果也有较好的提升;单独使用测高仪反演的结果较差,在峰高以下电子密度廓线和观测较一致,但峰高以上电子密度廓线和观测比较的结果较差,并且TEC结果和观测也有一定误差;而利用GPS和测高仪数据联合反演的结果最好,无论是反演的电子密度廓线还是TEC值都和观测最为接近.     

互补码在电离层探测中的应用

电离层探测仪一般采用m序列或Barker码序列调制的二相编码脉冲。但是这两种码元序列产生的编码脉冲信号经脉冲压缩后都存在较高的旁瓣。为降低脉冲压缩后信号的旁瓣,提出了在多普勒频移较低的电离层区域应用互补码作为二相编码脉冲的调制码元序列。互补码具有非常好的自相关特性,A序列和B码序自相关后相加,自相关和只有主瓣,不存在任何旁瓣。但是由于A,B相位编码脉冲并不同时发射,多普勒频移会降低互补码的脉冲压缩性能。仿真结果表明,当多普勒频移较低时,互补码相位编码脉冲回波脉压性能优越;但是当多普勒频移较高时,多普勒频移给A,B相位编码脉冲回波带来很大的相位差,使互补码脉冲压缩后指标严重恶化。     

Inversion of ionospheric electron density from GPS beacon observations

~~Inversion of Ionospheric Electron Density from GPS Beacon Observations~~SupportedbytheNationalNaturalScienceFoundationofChina(499840 0 1 )     

A study on ionospheric HF channel with bitemporal response and scattering function

At first the bitemporal response method is introduced to solve the scattering function of the ionospeeric channel. We can get the scattering function, as a function, of the group path time delay and Doppler frequency. Thus Doppler effect resulting from the continuous movement of the ionosphere is analyzed to study the characteristics of the various ionospheric irregularities and diturbance. many possible problems and correction are researched lastly. Foundation item: Supported by the National Natural Science Foundation of China (69571020) and the Research Fund for the Doctoral Program of Higher Education (RFDP1999048602) Biography: Chong Yan-wen(1972-), male, Ph. D. candidate, research direction: ionospheric modeling and inversion.     

Ionospheric responses to a total solar eclipse deduced by the GPS beacon observations

The total electron content (TEC) data during the total eclipse of March 9, 1997 were collected, which were observed by means of nine GPS receivers located at the eastern Asia. The responses of total TEC to the eclipse were analyzed. The results show that: 1) the eclipse led to apparent decrement in TEC that lasted for six to eight hours; 2) the maximum decrement occurred after the middle of the eclipse with time-delays varying from twenty minutes to about three hours; 3) the maximum absolute deviations of TEC on the eclipse day do not show a simple and consistent relationship to the maximum solar obscuration. Foundation item: Supported by the National Natural Science Foundation of China(49684002) Biography: CHEN An-hua (1976-), female, Master candidate. Research interests: studying ionosphere by GPS beacons.     

Novel adaptive Hatch filter to mitigate the effects of ionosphere and multipath on LAAS

It has been proven that carrier smoothing and differential global positioning system (DGPS) are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user. However, another issue coming with local area augmentation system (LAAS) is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath. Based on the errors analysis in carrier smoothing process, a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process. By conducting the simulation in LAAS and after compared with traditional Hatch filers, it reveals that not only the accuracy of differential correction, but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.     

Klobuchar模型的解读

对于单频GPS接收用户,电离层时延是重要的测距误差.Klobuchar模型是一种计算方便、实用可靠、能够有效改正GPS单频接收机的电离层延时误差的方法.展示模型的演绎分析和具体解算方法,对GPS单频机解算程序编写有一定帮助.     

Development of an ionospheric scintillation monitor using single frequency GPS receiver

Besides their intended use in radio navigation, global positioning system (GPS) satellite signals provide convenient radio beacons for ionospheric studies. Among other propagation phenomena, the ionosphere affects GPS signal propagation through amplitude scintillations that develop after radio waves propagation through ionospheric electron density irregularities. This paper outlines the design, testing, and results of a specialized GPS receiver to monitorL-band scintillations. The scintillation monitor system consists of a commercial GPS receiver development kit with its software designed to log signal strength and carrier phase from up to 12 channels at one sample per second rate. Other prime features of the monitor include the data compression transmission and processing. Here is the fact that they are inexpensive and compact and therefore can be readily proliferated. Foundation item: Supported by the National Natural Science Foundation of China (No. 49984001) Biography: Shu Di-fei (1973-), male, Master candidate, research direction: studying ionosphere on GPS beacons.     

超宽巷组合辅助电离层残差法北斗周跳探测与修复

根据北斗三频信号的特点及其组合观测值特性,详细阐述了一种新的非差观测值周跳探测与修复方法;该方法利用超宽巷组合(moulborne-wuebbena,M-W)组合观测值优点,对电离层残差法进行相应改进;并通过改进后的电离层残差法获取周跳的位置和大小。计算结果表明:该组合方法可以有效地探测和修复不同大小的周跳,而且适用于北斗三种不同类型卫星的信号处理,说明该算法具有较高精确性和可靠性。     

数字电离层建设的必要性

 实际应用中,针对不同的电离层电波传播效应,对不同的电离层参量特性,需采用不同手段的观测或不同参量模式的预测预报,解决不同的应用需求。这种"各自为阵"的方式不仅浪费资源,应用效果也较差。为此,本文提出了数字电离层概念,即综合利用中国已有及已经立项的空地多源立体探测体系,在电离层模式化研究的基础上,通过数据融合和数据同化,用数字化方式描述电离层状态参量过去、现在和未来的状况,高效统筹解决各类工程应用中对不同电离层参量的需求。介绍了数字电离层建设的必要性和国内外现状,重点说明了其主要内容和面临的技术瓶颈。