BOC调制技术研究

伽利略卫星导航系统是欧洲自主的、独立的全球多模式卫星定位导航系统，提供高精度、高可靠性的定位服务，同时它实现完全非军方控制、管理。伽利略系统采用BOC调制方式。现介绍BOC调制的性质及和BPSK调制方式相比较的优点。     

遗传算法抑制BOC(1,1)信号多径研究

针对传统方法无法有效抑制伽利略(Galileo) BOC (1,1)信号短时延多径的现状,将多径抑制问题转换为最优拟合问题,提出了一种有效估计短时延多径的方法。利用遗传算法不需要函数可导,且不易陷入局部最小值的特点,将其应用于最优拟合BOC (1,1)短时延多径信号的计算上,有效地减小了每个通道的伪距测量误差,提高接收机定位精度。给出应用该算法的具体步骤,仿真结果表明该方法可以更加有效地抑制短时延多径。     

伽利略E5段信号结构分析及仿真

本文介绍了伽利略卫星导航系统E5段的信号结构,新型调制方式BOC的基本原理和在E5中的应用,并对伽利略E5信号的结构作了分析和简化,验证了E5段的Alt BOC信号在接收端可以近似为一个QPSK信号,最后给出了对于Alt BOC信号的接收和捕获的Matlab仿真结果。     

对角加载对信号源数检测性能的改善

对角加载技术可抑制小特征值对自适应权值的影响来加速自适应波束形成器的收敛性以及抑制导向矢量误差的影响避免信号相消,该技术通常用于稳健的波束形成算法.基于对角加载技术,本文提出了一种信号源数目判定的改进方法,通过对角加载数据协方差阵,可以平滑小快拍数和空间色噪声时的噪声特征值分散程度从而减轻其对信号源数目估计的影响,证明了该估计器的强一致性,分析了加载量对信号源数目估计的影响.最后通过仿真以及实测数据比较了本文方法和已有方法的性能,验证了所提方法的有效性.     

伽利略EPTS中原子钟频率稳定度与噪声类型分析

本文对伽利略系统实验精确授时中心(EPTS)中四台原子钟的主要特性进行了分析.首先基于原子钟的信号模型和时域上的实验测量数据,用Allan方差对各原子钟的频率稳定度进行了计算与分析.其次运用最小二乘算法对短期和长期的时域稳定度数据进行线性拟合,根据拟合斜率鉴别了影响EPTS中各原子钟的主要噪声类型.实验结果表明,EPTS中具有高短期稳定度的氢原子钟和三台高长期稳定度的铯原子钟满足在GSTB-V1阶段产生实验伽利略系统时间(EGST)的设计要求.     

The Plausibility of Galileo's Tidal Theory

In Galileo's opinion, his most important argument for the Earth's motion was based on his theory of the tides that combined the Earth's rotation with its orbital motion so that it alternately accelerates and decelerates the sea. His theory deliberately ignored the Moon's influence, which at that time was generally regarded as occult. Galileo's confidence in his theory was strongly reinforced by its providing a mechanical model. That a theory that ignored the Moon's influence could seem plausible is confirmed by comparison with the theories of Bacon and Wallis. That Galileo's theory could seem plausible despite encountering difficulties is confirmed by comparison with Newton's theory, which is deeply flawed by its inclusion of a vertical response to the total tidal force. That many people now regard Galileo's theory as wrong is due to our having absorbed as natural Newton's idea of lunar attraction.     

伽利略E5波段信号扩频码基于VHDL的FPGA器件设计

介绍了伽利略卫星信号E5波段的基带信号结构,详细讲述了伽利略卫星信号中E5波段扩频码的结构和扩频码基于伪随机序列的线性移位寄存器的产生方法,给出了基于VHDL的FPGA器件设计方案以及modelsim仿真结果和signaltapII逻辑分析器捕获FPGA中的最终信号结果,由最终结果可知采用FPGA来实现伽利略伪卫星的E5,E1,L1波段的基带信号合成是非常简单易行的.     

GPS／Galileo双模捕获引擎的VLSI实现

随着卫星导航进入多星座时代,兼容GPS和Galileo的双模接收机成为目前卫星导航接收机设计的热点。捕获是卫星导航接收机基带信号处理的关键部分之一。本文通过对两种信号捕获算法的分析,提出了一种可以兼容GPS和Galileo信号的捕获引擎的VLSI结构。该结构兼顾了GPS和Galileo的信号特点,可以对GPS信号进行时域并行搜索和对Galileo信号进行时域部分并行搜索。最后给出了该结构各个组成单元的设计方法,在Altera公司的EP2S180FPGA器件上验证通过,并在0．18μm的CMOS工艺下综合,电路规模是3514231平方微米。     

Impact of Galileo commercial service on location-based service providers: business model analysis and policy implications

Today's mobile location-based services (LBSs) largely depend on a free-of-charge, best-effort positioning technology, called global positioning system, which is controlled by the US military. The European alternative Galileo will not only offer a similar best-effort system by 2020, but also a premium-rate service known as Galileo commercial service (CS). Galileo CS is planned to provide higher positioning accuracy, improved security due to signal authentication and service guarantee. While the technology behind Galileo is often studied, the impact of Galileo CS on the LBS marketplace is rarely discussed. In this article, we fill this gap by analysing how improved accuracy, authentication and service guarantee may impact the business models of LBS providers. We do so by interviewing service providers, policy makers and industry experts on what new services would be enabled; technological alternatives that may emerge in the coming years; and organisational and financial issues that service providers face when adopting such a premium-priced positioning signal. We find that a more accurate, secure and reliable global navigation satellite system signal enables a range of new LBSs, although several alternative technologies are emerging that may make Galileo CS obsolete before it is even launched. To convince the LBS providers to adopt Galileo CS, the institution operating Galileo should get governments on board early on for building trust and should consider progressive pricing schemes. Still, service providers are sceptical about adopting Galileo CS, and the hope to recoup any investments in Galileo may thus be in vain.