L5载波的信号质量分析

增加第三民用频率L5载波是GPS现代化措施中的一项,目前美国已经有4颗卫星具有L5观测值。从L5的信号结构上进行分析,应用L5载波的实际观测数据,与L1载波和L2载波相比较,L5载波不但在信噪比上得到提高,而且其多路径效应的影响也比较小,具有较好的数据观测质量。     

GPS第三频载波及民用码的信号质量分析

介绍了L5载波的特点,分析了L5载波对GPS测量的影响,用实测数据分析了三频载波的信噪比及各个民用码的噪声水平。     

L2C监测跟踪网信噪比SNR数据质量分析

本文从L2C监测跟踪网的数据出发,分析了其中六个监测站的信噪比(SNR)数据。首先分析了未调制L2C码卫星的L1载波和L2载波的信噪比,得出此时的L2的信噪比数值相对较小(L1载波的信噪比均值与L2的信噪比均值差异最大为19.1dB)且稳定性较差;随后分析了调制有L2C码的卫星的L1载波和L2载波的信噪比,得出现代化后的L2载波信噪比与L1载波的信噪比基本一致(两个信噪比之差基本上在5dB左右);进而得出结论:调制有L2C码的L2载波具有更好的数据稳定性和抗干扰能力,且具有易于捕获的特点。     

GPS现代化后L2载波的定位精度研究

利用实际采集的数据,从信噪比和定位残差上分析了L2载波的数据质量,指出GPS现代化后,用L2C码恢复的L2载波信噪比明显提高,与L2载波信噪比接近,两者的差值仅在5 dBHz以内;用L2 C码恢复的L2载波比GPS现代化前的L2载波的信噪比更加稳定,不容易受卫星高度角的影响;同时利用L2 C码恢复的L2载波的定位残差比没有L2 C码的L2裁波小,定位精度明显提高.     

现代化GPS信号的宽巷组合及其求解模糊度研究

结合GPS现代化计划的主要方面，即增加第3信号L5，给出了新的信号L5和L2载波组性组合的数学模型，重点对宽巷线性组合进行了研究，分别模拟计算并比较L5和L2以及L5和L1载波宽巷线性组合结果，最后利用宽巷组合求解模糊度，并得出结论。     

GPS SVN49卫星重新开启通过PRN24广播信号

GPS SVN49Block IIR-M卫星己于UTC时间2012年8月9日18:35,通过PRN24重新开始传播信号。信号当前的状态为unhealthy,并未包括在广播卫星历书中。SVN49卫星于2009年3月24日发射,在L1/L2卫星多路径问题被解决之前,一直没正式提供服务。虽然尚未包括在历书信息中,但一些IGS参考站己经接收到SVN49的信号。SVN49卫星在2009年3月28日到2011年5月6日期间,使用PRN01,在2012年2月2日至3月14日,使用PRN24。     

GPS现代化后L2载波的数据质量分析

从L2C码的信号结构、多路径效应和信噪比3个方面对实际采集到的观测数据进行分析,结果表明,新的L2C码采用了新的设计结构,其多路径效应与C/A码的多路径效应较为一致,且L2载波的信噪比得到明显提高。然后利用L1载波和L2载波分别求解双差模糊度,实验结果说明,加载了L2C码的L2载波和L1载波计算双差模糊度的效果一致,较原未加载L2C码的载波在模糊度解算效率上有显著的提高。     

GPS多频观测数据的模拟仿真

GPS现代化后增加了L5频率,多个频率观测值的使用可以组成更多的线性组合。但由于目前很难获取L5的实测载波数据,只能在双频载波的基础上通过多频载波相位观测值和伪距观测值的模拟模型获取L5载波的模拟数据。探讨了利用非差思想对L5进行数值模拟的方法,以相同方法模拟不同采样率下的L2载波数据并与实测的L2载波数据进行对比分析,验证了该模拟方法在高采样率下的可行性。     

L5载波相位观测值的模拟分析

GPS现代化计划目前只在几颗卫星上加入了L5信号,第三频率观测数据尚不能进行组网数据处理.如何验证现有多频理论的有效性,以及进行更深入、更广泛的多频数据处理理论应用研究,L5数据的获取成为一个重要问题.文中结合载波相位观测值之间的物理相关性,模拟L5载波相位观测值,对L5载波相位观测值的精度进行了分析,取得了一些有益的结论.     

GPS卫星导航信号体制的发展和设计比较研究

在GPS现代化计划的指导下，GPS卫星导航信号体制得到了不断发展和完善。本文分析总结了GPS卫星导航信号体制的发展和演进，研究了民用信号新增的L2C和L5，以及军用信号将采用的BOC调制，在此基础上对两个民用信号L2C和L5进行了比较研究。     

A multi-technique approach for characterizing the SVN49 signal anomaly, part 2: chip shape analysis

Due to a satellite internal reflection at the L5 test payload, the SVN49 (PRN1) GPS satellite exhibits a static multipath on the L1 and L2 signals, which results in elevation-dependent tracking errors for terrestrial receivers. Using a 30-m high-gain antenna, code and carrier phase measurements as well as raw in-phase and quadrature radio frequency samples have been collected during a series of zenith passes in mid-April 2010 to characterize the SVN49 multipath and its impact on common users. Following an analysis of the receiver tracking data and the IQ constellation provided in Part 1 of this study, the present Part 2 provides an in-depth investigation into chip shapes for the L1 and L2 signals. A single reflection model is found to be compatible with the observed chip shape distortions and key parameters for an elevation dependent multipath model are derived. A good agreement is found between multipath parameters derived independently from raw IQ-samples and measurements of a so-called Vision Correlator. The chip shapes and their observed variation with elevation can be used to predict the multipath response of different correlator types within a tracking receiver. The multipath model itself is suitable for implementation in a signal simulator and thus enables laboratory testing of actual receiver hardware.     

Ambiguity resolution for triple-frequency geometry-free and ionosphere-free combination tested with real data

The recent GPS Block IIF satellites SVN62 and SVN63 and the Galileo satellites GIOVE-A, GIOVE-B, PFM and FM2 already send signals on more than two frequencies, and more GNSS satellites will provide tracking data on at least three frequencies in the near future. In this paper, a simplified general method for ambiguity resolution minimizing the noise level for the triple-frequency geometry-free (GF) and ionosphere-free (IF) linear combinations is presented, where differently scaled code noise on the three frequencies was introduced. For the third of three required linear combinations, the most demanding one in triple-frequency ambiguity resolution, we developed a general method using the ambiguity-corrected phase observations without any constraints to search for the optimal GF and IF linear combination. We analytically demonstrate that the noise level of this third linear combination only depends on the three frequencies. The investigation concerning this frequency-dependent noise factor was performed for GPS, Galileo and Compass frequency triplets. We verified the theoretical derivations with real triple-frequency GPS and Galileo data from the Multi-GNSS Experiment (M–GEX) of the International GNSS Service (IGS). The data of about 30 M–GEX stations around the world over 11 days from 29 April 2012 to 9 May 2012 were used for the test. For the third linear combinaton using Galileo E1, E5b and E5a, which is expected to have the worst performance among all the GNSS frequency triplets in our investigation, the formal errors of the estimated ambiguities are in most cases below 0.2 cycles after 400 observation epochs. If more GPS satellites sending signals on three frequencies or more stations tracking Galileo E6 signal are available in the future, an improvement by a factor of two to three can be expected.     

基于GPS新型L5信号的地表雪深反演研究

利用GPS多路径反射信号测量地表雪深具有全天候和高时空分辨率的特点,因此其可作为一种代替气象站监测雪深的新手段。然而,先前大多数研究仅使用了GPS L1和L2C波段信噪比数据探测积雪深度。为验证新型的L5信号在雪深反演方面的优越性,本文阐述了GPS-R技术反演雪深的原理,利用Lomb-Scargle周期图法所处理的受积雪表层影响的信噪比数据计算了频谱振幅强度,通过获取频谱特征值与天线高度的关系求解雪深值,最后分别与L1反演结果和实测雪深数据进行了对比。试验结果表明：与现有的GPS-R测量雪深结果相比,利用新型的L5反射信号反演地表雪深的精度更佳;采用GPS-R技术探测雪深对把握测站区域内的雪深变化情况和淡水资源储量具有重要价值。     

Apparent clock variations of the Block IIF-1 (SVN62) GPS satellite

The Block IIF satellites feature a new generation of high-quality rubidium clocks for time and frequency keeping and are the first GPS satellites transmitting operational navigation signals on three distinct frequencies. We investigate apparent clock offset variations for the Block IIF-1 (SVN62) spacecraft that have been identified in L1/L2 clock solutions as well as the L1/L5-minus-L1/L2 clock difference. With peak-to-peak amplitudes of 10?C40?cm, these variations are of relevance for future precision point positioning applications and ionospheric analyses. A proper characterization and understanding is required to fully benefit from the quality of the new signals and clocks. The analysis covers a period of 8?months following the routine payload activation and is based on GPS orbit and clock products generated by the CODE analysis center of the International GNSS Service (IGS) as well as triple-frequency observations collected with the CONGO network. Based on a harmonic analysis, empirical models are presented that describe the sub-daily variation of the clock offset and the inter-frequency clock difference. These contribute to a better clock predictability at timescales of several hours and enable a consistent use of L1/L2 clock products in L1/L5-based positioning.     

GPS中频信号快速捕获技术分析

为解决GPS中频信号快速捕获问题,在介绍GPS码相位和载频信号捕获原理的基础上,重点阐述了基于FFT的并行GPS中频信号快速捕获方法,同时在非相干累加、接收信噪比、先验信息等方面分析了提高中频信号快速捕获的可能性,最后利用一组GPS实测数据对上述分析进行了的仿真计算。仿真结果表明基于FFT技术的中频信号快速捕获方法具有抗干扰、捕获速度快和检测低信噪比信号的能力,可以满足GPS软件接收机定位的要求。     

A multi-technique approach for characterizing the SVN49 signal anomaly, part 1: receiver tracking and IQ constellation

A characterization of the signal anomaly of SVN49 is presented. A mathematical model is developed to relate the observed multipath to the internal signal reflection. The analyses provided are based on measurements, which have been collected during a dedicated tracking campaign with a 30-m dish antenna. Data on the L1 and L2 frequency have been collected with four different receivers. In addition, IQ samples have been recorded directly with a spectrum analyzer. The multipath combination of the receiver measurements on L1 and L2 is analyzed to demonstrate the effect of the signal reflections on different correlator spacing. The capability to suppress the signal reflection with receiver multipath mitigation methods is demonstrated. Finally, preliminary estimates of the attenuation, delay, and phase shift over elevation are obtained from an IQ sample analysis.     

TK算法在GPS中的新应用

讨论了TK算法的原理和在GPS中TK算法的新应用。用TK算法估算出GPS多径信号相对于直射信号的码片延迟,使GPS直射信号经过一定的延迟后,与反射信号进行叠加,提高了直射信号的载噪比,进而达到反射信号增强直射信号的作用。验证了这一算法和结论。     

GPS干扰监测技术

随着GPS导航定位技术的日臻完善,其应用范围也越来越广,定位精度不断提高,GPS干扰监测和抗干扰措施一直是该领域的热门研究课题。本文从干扰信号监测和卫星信号监测两个角度研究分析了GPS干扰监测中的重要技术与实现方法。     

卫星信号发射时刻的无偏恢复

卫星信号发射时刻在导航定位中是一个重要的参数,但是在城市峡谷等弱信号条件下,接收机可能完成不了所有卫星信号发射时刻的组装。在伪距定位中卫星信号发射时刻的组装和粗时段导航中卫星信号发射时刻的恢复(有偏)技术基础上,提出一种无偏的卫星信号发射时刻恢复方法,前提是卫星至少能完成一颗星的伪距测量,并且具有150km误差范围内的先验位置和辅助星历。利用BDS B1和GPS L1中频数据在软件接收机平台进行了BDS,GPS信号发射时刻无偏恢复验证实验证明了方法的有效性。     

测量型GPS仪器比较

以科学的方法对Trimble、Topcon、南方测绘三个厂家GPS信号接收机和数据后处理软件进行比较。首先从GPS的发展历史和现状及其存在的问题进行分析研究,结合GPS系统和信号接收机的原理,对GPS结构等不同的方面进行分析比较,然后比较分析了各型号GPS的物理指标、精度指标、性能和价格,并对各型号GPS对应的数据后处理软件进行了实验分析,最后通过实验分析得出结论。