为了建立电离层延迟模型来确定电离层对电磁波传播的影响，以电子密度的分布为研究对象，根据基本折射理论分析电离层的色散效应，对电离层延迟原因进行分析，研究电离层总电子含量TEC（Total Electron Content）对其影响，并且此影响与卫星信号频率有关。利用GPS双频接收机和投影函数建立电离层的单层VTEC（Vertical Total Electron Content）多项式模型，在大庆进行实地连续观测获取相关数据，建立了大庆地区的电离层延迟模型。总结VTEC昼夜变化规律，并对结果进行了分析和说明。

In order to determine the effect of ionosphere on electromagnetic propagation by setting up the ionospheric delay model,we take the distribution of electron density for studying object,analyse the dispersion effect of ionosphere according to the basic refraction theory,and analyse the cause of the ionospheric delay.We study the influence of total electron content (TEC)in ionosphere on it,and such effect is related to the satellite signal frequency.Then we use dual-frequency GPS receiver and projection function to build the ionospheric polynomial model for vertical total electron content (VTEC),and carry out consecutive filed observation to collect the correlated data in Daqing,and build the ionospheric delay model in this region.After that,we summarise the rule of diurnal variation of VTEC.The results are then analysed and explained.

本文讨论了电离层垂直电子总含量比较法和单频单点定位法两种电离层模型参数改正精度评估方法,介绍了北斗系统发播的电离层模型参数的使用方法,基于欧州定轨中心提供的全球电离层数据评估北斗系统发播的电离层模型参数精度,分析结果表明:北斗系统发播的Klobuchar电离层模型参数在西安地区的改正比例,白天为80%左右,夜间为75%左右。

This article discussed the VTEC comparison method and the single frequency point positioning method for evaluating ionospheric parameter correction precision ,intro-duced the using method of ionosphere parameters of BDS ephemeris ,and assessed the BDS’s ionosphere parameters accuracy ,based on the GIM ionosphere model of CODE .T he analysis results show that in Xi''an area the BDS’s Klobuchar model parameters accuracy is about 80%during the day ,and about 75% during at night .

对于GPS单频用户而言，电离层延迟是最重要的误差来源之一。GPS系统使用Klobuchar模型对电离层延迟进行改正，其改正数从370组常数中选取。目前全球分布的GPS测站可以获得高精度的全球电离层监测结果，GPS为什么不发播采用实测数据计算得到的Klobuchar模型参数呢？本文针对这一问题进行分析。首先，对欧洲定轨中心CODE提供的全球电离层图GIM预报COPG电离层进行精度评估，然后根据COPG电离层进行Klobuchar模型参数拟合，并利用IGS提供的事后高精度电离层图进行精度分析，最后将不同的电离层模型参数应用于单点定位以评估其对单频用户的影响。分析结果表明，采用全球实测数据计算的电离层模型参数与导航电文中发播的电离层模型参数精度相当，为55％左右。而仅采用地磁纬度45°S以北的数据拟合得到的模型参数，其电离层改正精度有明显提升，可达65％左右，但其对单频用户定位精度改善不明显。

To GPS single‐frequency users ,the ionospheric delay is one of the most important sources of errors .GPS uses Klobuchar model ,whose corrections come from 370 groups of constants derived from empirical models and historical data ,to correct the ionospheric delay currently stations distributed all over the world can provide ionosphere monitoring results with high precision , why GPS doesn’ t broadcast Klobuchar model parameters calculated with observed data?This article focuses on this question .Firstly , the precision of predicted global ionosphere maps ,COPG ,provided by center for orbit determination in Europe (CODE) is estimated .Secondly ,the Klobuchar model parameters are fitted with COPG .Then the parameters’ precision is assessed with global ionosphere maps provided by IGS .Finally single point positioning is done using different Klobuchar parameters to evaluate their influences on GPS single‐frequency users .Results show that restricted by Klobuchar model with 8 p

电离层是一种典型的色散介质,会对导航信号产生延迟,且不同频点处的电离层延迟互不相同。实际应用中通常只考虑接收信号中心频点处的电离层延迟,而忽略信号带宽范围内的电离层色散特性。建立了电离层色散特性的对导航信号接收的影响分析模型,并定量地分析了电离层色散效应对BPSK(10)、BOC(14,2)以及AltBOC(15,10)等宽带导航信号的影响。分析表明电离层色散效应对BPSK(10)信号的影响可忽略不计,对高阶BOC信号会产生一定程度的与电离层特性相关的相关损耗及载波跟踪偏差,其中AltBOC(15,10)产生的相关损耗最高约1.4dB,载波相位跟踪偏差最高约0.374π。

Ionosphere is a typical dispersive medium,which may cause frequency depended delay to navigation signal.In the practical applications,the ionosphere delay between signals at different frequencies is considered only,while the effect of ionosphere dispersion on the receiving for a single navigation signal is usually ignored.A module was established to analyze the effect of ionosphere dispersion.Base on this module,the effect of ionosphere dispersion on some typical wide-band navigation signals was analyzed,such as BPSK(10),BOC(14,2),AltBOC (15,10)signals.The analysis results indicate that the effect on BPSK(10)signal can be ignored,but some correlation loss and carrier phase tracking error will be introduced into the track of high order BOC signals,such as BOC(14,2)signal and AltBOC(15,10)signal,and the correlation loss and carrier phase tacking error of AltBOC(15,10)can be 1.4dB and 0.185 cycles separately.

"极区电急流天线"辐射依赖于低电离层D/E区背景电急流,而高电离层F区极低频调制加热,可产生抗磁性电流,形成极低频波辐射源。利用电离层F区一维时变加热数值模型,采用全波解算法研究高纬Troms(69.59°N,19.23°E)地区电离层F区极低频调制加热。模拟结果表明,极区高电离层激发的极低频波与极区低电离层激发的结果不同。加热泵波的有效辐射功率(effective radiated power,ERP)、调制频率及电离层背景对极低频波强度有着重要影响。

Polar ionospheric heaters operated by HARRP and EISCAT have generated extremely low frequency waves by modulating the auroral electrojet at D and E region altitudes .However , the auroral electrojet often varies over time and is not always present .Alternatively, modulated F-region HF heating can generate ionospheric diamagnetic cur-rent, and the periodic modulation results in a magnetic moment that radiates extremely low frequency waves .Based on a one-dimensional time physical model of polar ionospheric heating and a full-wave model , we analyzed the fea-tures of extremely low frequency waves over Troms?(69.59°N, 19.23°E).The results showed that extremely low frequency waves on the ground are different from lower ionospheric modulation , i.e., radiation of polar electrojet antenna.Furthermore, effective radiated power (ERP), modulated frequency, and ionospheric background, have significant influence on the generated extremely low frequency wave .