GPS导航卫星播发的信号是什么样的？（下）

GPS信号中导航电文（NAVmessage）包含卫星星历（卫星精确的轨道位置信息）、星载原子钟修正数据、卫星历书（卫星近似的轨道位置信息）、电离层时延改正、卫星健康状态、C／A码引导捕获P码的信息。将这些信息以二进制码的形式编码,数据采用不归零制（NRZ）的二进制码,数据码码速率为50bit／s的为方波信号,     

GPS自主完好性监测可用性预测系统的设计

GPS自主完好性监测可用性预测系统提前计算GPS卫星的RAIM可用性,可以为机场服务。该预测系统使用GPS卫星历书、NANU报、NOTAM报和机场信息对GPS卫星的RAIM可用性进行预测。该预测系统的预测结果准确,易于工程应用。     

通用航空GPS/BDS机载设备研究及设计

本文描述了 GPS/BDS 机载设备的总体架构和详细设计方法。基带处理部分,给出了基于 PMF-FFT 的捕获算法。基带处理电路主要完成对射频通道传送过来的中频信号进行采样、 数字滤波、信号处理、功能解算等功能。GPS/BDS 机载设备具备兼容 GPS、BDS 和 GLONASS 卫星导航系统的能力;具备卫星导航系统历书、星历、原始测量数据输出、RAIM 处理、差分处理、多种数据格式输出、BIT 系统自检、工作状态提示等能力。     

同步卫星位置的外推算法应用

在同步卫星测距定位系统中，星历发布整分点的卫星位置和速度。本文利用卫星动力学方程，用线性或龙格－库塔法外推，得到测距时卫星的位置，结合该星历发布的实际数据，在星历数据未丢失和丢失时，比较了两种外推方法的精度，并研究了外推步长和各种引力因素对卫星位置外推精度的影响。     

GNSS空间信号精度评估方法

空间信号(SIS)精度是卫星导航系统的性能之一。针对目前精度评估模型存在的问题,提出了分段式SIS用户测距误差(URE)评估模型,并研究了SIS用户测速误差(URRE)、用户测加速度误差(URAE)评估模型,利用广播星历和精密星历评估了GPS和BDS的SIS精度性能。结果表明,除BDS C02卫星的URE以及GPS PRN10卫星的URAE略大以外,其余GPS和BDS卫星的SIS URE,URRE和URAE均符合各自系统的指标,验证了所提精度评估方法的有效性。     

GPS卫星精密星历插值在靶场数据处理中的比较

为了提高目标在地心坐标系的绝对定位精度,降低星历误差对单点定位和相对定位的影响,必须采用GPS卫星的精密星历。精密星历在GPS数据处理时需构造合适的插值模型进行内插,才能得到任意时刻卫星的位置。分析比较了2种经典的多项式插值及逐次线性插值的Neville算法的数学模型及插值结果,探讨了3种插值算法的适用范围,得到了适用于靶场精密星历的处理的插值方法。     

高动态GPS信号模拟器卫星星历产生方法研究

星历产生是高动态GPS信号模拟器研制中一个很重要的组成部分,星历部分所提供的参数是否正确直接影 响到模拟器所能提供的仿真信号精度。在分析了GPS卫星导航电文结构的基础上,确定了部分参数在模拟器中的选取,实现 了电文子帧的校验算法及星钟误差的计算方法,并提出了建立在时间外推基础上的星历产生方法。     

GPS星历、在轨描述和位置算法

本文介绍了GPS星历、在轨描述、在轨位置算法,以及GPS卫星全球定位系统的发展与现况,并认为,GPS系统建立30余年来,卫星不断更新换代,稳步增强卫星导航性能;信号军民巧分离,力保占据卫星导航市场的高份额;系统不断采用新技术,是很值得我们建设Compass系统学习的。     

一种新插值法在卫星导航广播星历中的应用简

导航卫星广播星历是卫星导航定位的基础,要求有较高的精度和实时性.利用广义延拓插值法来拟合GPS导航卫星轨道,插值系数作为广播星历的参数发播,是一种新的广播星历形式.而且具有精度高,计算快捷等特点,另外对于具有其他多种轨道类型共存的导航系统来说也具有一定的参考意义.     

基于VC++的GPS软件接收机设计

由于GPS软件接收机具有需要硬件资源极少、可移植性强、开发新算法成本低等诸多优点,成为了新一代GPS接收机研制的热点.完成了基于快速傅里叶变换(FFT)算法的卫星信号的捕获算法、基于混合载波跟踪环的载波跟踪和码跟踪算法、卫星星历数据的提取及卫星状态解算算法和伪距测量算法等算法的仿真验证,介绍了基于VC++的GPS软件接收机的设计方法和过程.该软件接收机可以输出各个通道跟踪到卫星信号的载波频率、伪码频率及伪距,卫星星历及卫星状态,接收机的位置、速度信息以及各种DOP值等诸多信息.最后,给出了所开发的GPS软件接收机在实际GPS数字中频信号下的定位结果.结果表明,该软件接收机的定位误差在20 m以内.该GPS软件接收机系统采用纯软件的方法实现了硬件GPS接收机数字中频信号后的所有功能,算法修改灵活,可为进一步研究GPS接收机的各种算法提供一种方便快捷的仿真平台.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.