Galileo双频接收机及其关键模块的设计

为设计Galileo双频接收机,对Galileo系统空间信号的特性进行了描述,通过比较Galileo系统与GPS的不同,论述了Galileo系统的优点。最终再结合已有接收机技术,给出了一种实用的基于E5频段Galileo双频接收机结构体系的设计,并重点分析了下变频模块和信号捕获与跟踪模块的设计。     

基于BDS-3、GPS和Galileo重叠频率观测值的紧组合RTK定位方法

基于BDS-3、GPS和Galileo的重叠频率(BDS-3 B1C/B2a、GPS L1/L5、Galileo E1/E5a)观测值,分析了重叠频率观测值间的差分系统间偏差(DISB)稳定性,在此基础上提出了顾及系统间偏差的三系统紧组合RTK定位方法,并采用实测数据对常规松组合和紧组合模型的模糊度解算性能和定位精度进行了对比分析。分析结果表明,对于用相同类型接收机组成的基线,3个系统重叠频率观测值间的伪距和载波DISB均接近于零,可直接忽略。相比常规各系统选择各自参考卫星的松组合模型,采用共同参考卫星的系统间紧组合模型单历元模糊度解算的模型强度、固定率、固定准确率均有一定的改善,尤其在高截止高度角的不良观测环境下改进明显;在定位精度方面,紧组合模型也有一定的提升,当截止高度角为40°时,N/E/U 3个方向上的定位精度分别可提高15.0%、11.8%和19.4%。     

一种基于DDS技术的Galileo接收机设计

针对新一代卫星导航系统-Galileo系统,提出了一种应用数字无线电（Digital Radio）技术和直接数字综合（Direct Digital Synthesis,DDS）技术的Galileo用户接收机原理架构。详细阐述了射频前端模块设计和基带信号处理模块设计,给出了射频／中频链路的频点规划、A／D采样方法,基带处理模块的信号捕获、伪码跟踪及载波跟踪算法;并采用结构仿真对系统架构和信号的捕获与跟踪算法进行了严格的仿真验证。仿真系统实现了E5波段Galileo信号的初始捕获,并成功跟踪了200Hz／s的多普勒一次变化和1000Hz／s^2的多普勒二次变化。     

GPS和Galileo导航电文设计分析

导航电文设计的优劣直接影响卫星导航定位的可靠性,该文以GPS和Galileo导航系统的导航电文设计为例,汇总了GPS和Galileo系统导航电文设计的最新成果,比较分析GPS传统的导航电文格式NAV和新的民用导航电文格式CNAV以及Galileo系统的导航电文,并对导航电文数据结构、编排方式、差错控制以及播发方式等方面的性能进行评估,进行导航电文的优化设计,以期为我国北斗导航系统的电文设计提供借鉴。     

Monte Carlo simulations of the Galileo energetic particle detector

Monte Carlo radiation transport studies have been performed for the Galileo spacecraft energetic particle detector (EPD) in order to study its response to energetic electrons and protons. Three-dimensional Monte Carlo radiation transport codes, MCNP version 4B (for electrons) and MCNPX version 2.2.3 (for protons), were used throughout the study. The results are presented in the form of “geometric factors” for the high-energy channels studied in this paper: B1, DC2, and DC3 for electrons and B0, DC0, and DC1 for protons. The geometric factor is the energy-dependent detector response function that relates the incident particle fluxes to instrument count rates. The trend of actual data measured by the EPD was successfully reproduced using the geometric factors obtained in this study.     

Early TMM in Le Mecaniche by Galileo Galilei in 1593

In this paper the work on the Theory of Machines by Galilei is reviewed and interpreted. The small treatise Le Mecaniche can be considered of fundamental significance in the History of Mechanical Engineering since it was written for a first academic course on TMM, and it used modern concepts.     

Architecture and Mathematics: Between Hubris and Restraint

The introduction of calculus-based mathematics in the 18th century proved fatal for the relationship of mathematics and architecture. As Antoine Picon, Professor of History of Architecture and Technology at Harvard Graduate School of Design, highlights, when geometry was superseded by calculus it resulted in an ensuing estrangement from architecture, an alienation that has persisted even with the widespread introduction of computation. It is a liaison that Picon characterises as having shifted between hubris and restraint. Copyright © 2011 John Wiley & Sons, Ltd.     

Mathematics and the Sensible World: Representing,Constructing, Simulating

The Paris-based scientific historian Amy Dahan-Dalmedico asks why a knowledge of numbers, algebra and abstract forms should be key to our understanding of the sensible world. As she reveals, mathematics, like the world itself, has shifted and fluctuated over time since its earliest origins in ancient Egypt. Evolving and morphing as a discipline, it has covered a diverse range of practices and theories. Copyright © 2011 John Wiley & Sons, Ltd.     

多星分离的ADAMS仿真

以长征火箭发射伽利略星为应用背景,运用ADAMS软件对三星分离的近场情况进行了仿真分析.详细介绍了分离分析中建立星箭模型的ADAMS描述、仿真过程控制以及各偏差因素对分离过程影响的分析方法.同时,运用ADAMS仿真可以方便地对多星分离的故障模式进行分析,对数值仿真难以实现的碰撞问题进行直观的检测.