RS码的时域编码频域译码技术

通过对于RS码的时域编码／频域译码的算法进行分析,找到了它们的不同之处及转换方法,得出了时域编码／频域译码的混合编译码方法,提高了运算速度和纠错能力。     

应用傅里叶时间谱方法求解二维跨音速流动问题解的精度研究

为了从时间离散精度的角度评估傅里叶时间谱方法的实际计算效率,对用该方法求解二维跨音速流动问题的解进行了精度研究。通过求解Euler方程模拟俯仰振动NACA0012翼型的周期性非定常流动。结果表明:傅里叶时间谱方法可以使用很大的时间间隔较为准确地模拟有激波存在的周期性跨音速流动;对于此类流动问题,相比二阶向后差分公式法,傅里叶时间谱方法在预测翼型表面压力系数积分量特别是升力系数的时间变化规律方面具有明显的计算效率优势;用于模拟翼型表面压力系数自身的时间变化规律时,傅里叶时间谱方法具有不低于二阶向后差分公式法的计算效率。     

北斗/GNSS高精度时频终端测试方法探讨

基于虚拟仪器技术、网络技术和批量化测量技术,探讨北斗/GNSS高精度时频应用终端的测试手段;提出应用测试模块化和VXI/PXI/LXI总线技术的测试设计方案,该方案具有多路标准时间频率参考信号一致性设计和网络远程测试校准设计;同时,提出北斗/GNSS高精度时频终端测试校准系统的结构设计及其应用模式。这将能有效提高北斗/GNSS时频终端测试的集成化和智能化水平。     

Digital signal processing and numerical analysis for radar in geophysical applications

Numerical solutions for signal processing are described in this work as a contribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar’s range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated.     

Geostationary orbit determination using SATRE

A new strategy of precise orbit determination (POD) for GEO (Geostationary Earth Orbit) satellite using SATRE (SAtellite Time and Ranging Equipment) is presented. Two observation modes are proposed and different channels of the same instruments are used to construct different observation modes, one mode receiving time signals from their own station and the other mode receiving time signals from each other for two stations called pairs of combined observations. Using data from such a tracking network in China, the results for both modes are compared. The precise orbit determination for the Sino-1 satellite using the data from 6 June 2005 to 13 June 2005 has been carried out in this work. The RMS (Root-Mean-Square) of observing residuals for 3-day solutions with the former mode is better than 9.1 cm. The RMS of observing residuals for 3-day solutions with the latter mode is better than 4.8 cm, much better than the former mode. Orbital overlapping (3-day orbit solution with 1-day orbit overlap) tests show that the RMS of the orbit difference for the former mode is 0.16 m in the radial direction, 0.53 m in the along-track direction, 0.97 m in the cross-track direction and 1.12 m in the 3-dimension position and the RMS of the orbit difference for the latter mode is 0.36 m in the radial direction, 0.89 m in the along-track direction, 1.18 m in the cross-track direction and 1.52 m in the 3-dimension position, almost the same as the former mode. All the experiments indicate that a meter-level accuracy of orbit determination for geostationary satellite is achievable.     

时间频率设备自动监控系统的设计与实现CSCD

针对时间频率实验室设备实时监控的需求,在Microsoft NET平台上结合C++语言和Microsoft SQL server数据库技术,构建了时间频率设备自动监控系统。该系统可以实时监测设备的运行状态,并远程设置相关参数,在设备运行异常时,系统可自动弹出报警信息。实际应用表明系统具有较好的实用性、可维护性,为时间频率实验室的有序运行提供了保障。     

π-TFSK时频调制信号状态迁移的分析

本文主要对π－ＴＦＳＫ时频调制信号的状态迁移进行分析。首先,从数学模型出发,对π－ＴＦＳＫ时频调制信号的状态进行分析;然后,推出了该信号的状态迁移图;最后求出了π－ＴＦＳＫ时频调制信号的状态迁移矩阵。     

基于北斗三号的长基线共视时间比对

卫星导航共视时间比对一直是远距离时间比对的重要方法之一。使用我国最新发射的北斗三号全球导航卫星,基于中科院国家授时中心（NTSC）和捷克光电研究院（TP）各自的时间产生和保持系统,开展了中捷北斗三号长基线共视时间比对试验。本文对中捷两站各自的北斗卫星可视数及其卫星高度角情况进行了统计分析,利用Vondark滤波对时间比对结果进行了降噪处理,最后将北斗三号共视时间比对结果与北斗二号及GPS共视时间比对结果进行了比较。结果表明：北斗三号在当前全球组网阶段中捷共视可视卫星数比北斗二号还少的情况下,其共视时间比对精度达到1.16ns,较北斗二号提升约19%,与GPS更为接近。     

我国BPL时号的频率控制系统及结果分析

根据我国现行ＢＰＬ时号的频率控制系统,分析ＴＢＰＬ时号频率控制系统的缺陷,对目前ＢＰＬ时号的频率稳定性进行了评价,提出了一种新的频率控制方案。     

互联网上计算机时间传递系统设计方案及实验结果分析

计算机互联网的发展,使信息的传递更加方便、快捷。在时间频率用户中,中、低准确度的用户占很大比例,计算机互联网时间传递已经成为一个重要的手段。中国的网络授时系统从２０００年１月开通以来,近万人访问了授时网站ｈｔｔｐ：／／ｋｘｚｈ．ｓｘｓｏ．ａｃ．ｃｎ或其镜像站点ｈｔｔｐ：／／Ｂｅｉｊｉｎｇｔｉｍｅ．１２６．ｃｏｍ。介绍了国家授时中心网络授时系统的设计要点,给出了网络授时传递时间准确度的测量方法,分析了网络授时实验结果。