基于GPS的目标飞行时间异地高精度测量技术

针对远程目标异地作用的特性以及异地时间测量对时间统一标准的严格要求,提出了一种基于GPS的高精度异地目标光信号时间测量系统.该系统将GPS授时与本地温补晶振时钟结合起来,利用GPS授时秒脉冲1 pps进行时间同步,由本地时钟结合GPS的标准时间测量出飞行目标启动和停止的精确时间及时间间隔;同时设计了高精度的授时方案,对GPS秒脉冲进行监控和补偿,有效提高了系统的可靠性.实验表明,该系统测量在400 s内所产生的累积测量误差小于300μs,等效精度达到7.5×10-7.     

基于TW-TOA的高精度室内定位系统的设计

基于超宽带(UWB)技术的定位系统以性价比高、抗干扰能力强等优势在室内无线定位系统中占有重要地位。UWB无线定位的测距误差受晶振偏差和多径效应等影响。基于双向到达时间(TW-TOA)的方法设计了一种高精度UWB室内定位系统,首先介绍了UWB定位系统原理,然后分析系统时钟偏差对测距误差的影响,进行软硬件设计,为减轻多径影响系统采用BP神经网络进行数据处理,最后进行测试和验证。测试结果表明:该定位系统的定位精度高,多径影响小。     

电子停车计时收费表检定装置的研制

文中根据最新实施的JJGl010—2013《电子停车计时收费表》规程要求,采用高精度温补晶振计时和北斗／GPS授时技术,采用多通道方式,设计了一套电子停车计时收费表检定装置。该装置能对检定规程所要求的时钟日差、当前时刻误差、停车计时误差、扣费正确性项目进行检定。     

出租汽车计价器永久时钟误差分析

本文通过对出租车计价器永久时钟误差分析 ,解释了CJ5 0 2 4— 1997电子式出租汽车计价器行业标准对永久时钟允许误差所作规定的合理性 ,并为如何控制这一误差提供了一定的理论依据     

基于非稳定时间源的IEEE1588时钟同步技术分析与改进

针对IEEE1588标准对网络环境稳定性的较高要求,提出一种在时间源不严格稳定时的改进方法。通过在阈值范围内信任标准信号进行时钟调相并跟踪相位变化进行晶振频率修正,避免不稳定信号对同步精度及系统稳定造成影响。以Matlab结合VC++的软件仿真和Modelsim的硬件仿真表明,该方法使同步精度得到了提高,并保证了从时钟的稳定运行。     

对《出租汽车计价器检定规程》(JJG-2009)的一点建议

出租汽车在营运或进行出租汽车计价器使用误差检定中,经常发现计价器永久时钟误差过大,造成乘客乘坐出租汽车时应付金额不准确所引发的纠纷。建议在开展出租汽车使用误差检定时,增加永久时钟的检定。     

基于GPIB接口的时钟测试仪内部晶振频率自动测试系统

介绍时钟测试仪,给出了基于GPIB接口的时钟测试仪内部晶振频率自动测试系统的硬件平台构建和自动测试实现方法,并详细讨论了实现过程中仪器控制、数据采集、数据处理和输出实现,最后给出了性能分析。     

小议出租车计价器的永久时钟超差现象

我们在出租车计价器的日常周检中经常碰到一些计价器上的永久时钟误差超差的现象。此种情况往往会产生因夜间加价收费而引发的纠纷。比如2005年1月31日《春城晚报》曾刊登了一篇《出租车夜间收费现“黑洞”——谁为夜间提前收费埋单》的文章。文章中写到一乘客所乘坐的出租车计价器上的时钟比标准时间快了12分钟。未到22：00就进入夜间收费状态。当乘客向司机提出质疑时。司机解释说：该计价器上的时钟从出厂起就每月快一分钟，对于这一点，我也没有办法。     

出租车计价器时钟线路常见故障检查及处理

出租车计价器时钟线路一般由时钟芯片及外围振荡线路构成 ,以并行或串行方式与ＣＰＵ交换信息。一旦时钟线路出现故障 ,将影响计价器计时计费准确性 ,应及时加以修理。以下就时钟线路一些常见故障的检查及处理方法作一介绍。一、备用电池电压过低当计价器不计时、计时不准及内存时钟参数保护不住时 ,首先应检查备用电池电压 ,若低于时钟芯片额定工作电压范围应对电池进行更换。下表列出了三种时钟芯片的额定工作电压范围 ,以供参考。对锂电池可在负载情况下用万用表直接测量其电压加以判断。而对于镍镉电池 ,如果测量前计价器已工作一段时间…     

一种基于FPGA的压控晶振同步频率控制系统

晶振时钟信号存在长期稳定度差和累积误差的问题。本文是利用GPs提供的1pps秒脉冲信号,在FPGA的基础上利用干扰秒脉冲信号消除和偏差频率平均运算等方法,减少外围电路,既消减了GPS时钟信号的随机干扰误差,又消除了本地晶振时钟信号的累计误差,从而控制本地压控晶振输出频率,提高晶振的长期稳定性。     

基于熵权法的卫星钟差预报研究

星载原子钟是全球导航卫星系统的核心设备之一,其性能及钟差预报精度直接决定着导航定位授时服务的精度。针对卫星钟差组合预报技术中子模型权值难以确定的问题,将熵权法引入到北斗卫星钟差组合预报中。对卫星钟差数据中的粗差、钟跳等异常值进行相频域组合探测,并使用滑动拉格朗日内插法进行修补,得到“干净”钟差序列。以灰色模型和二次多项式模型作为基础模型,构建基于信息熵这一新的评价指标的钟差组合模型,建立北斗卫星钟差熵权组合预报模型。使用武汉大学IGS数据中心发布的北斗精密钟差数据产品,分别进行了连续多天的短期预报和中长期预报试验,多天的平均试验结果验证了熵权组合模型在北斗卫星钟差预报精度和稳定性方面较传统组合模型均存在一定优势。     

基于光纤双向时间传递实时驯服铷钟的远程时间溯源

为了提高铷原子钟的远程时间溯源性能,在中国计量科学研究院TWOTFT链路的基础上,实施了对铷原子钟的高精密准实时驯服实验,驯服间隔分别为16,5,1min,实现了基于TWOTFT的远程时间溯源原理验证。实验结果表明:在远程时间溯源中,TWOTFT相比GNSS时间频率传递效果更优,且1min TWOTFT远程时间溯源效果最优,98.67%的时差绝对值在0.5ns内,时间稳定度和频率稳定度分别为2.5×10^-11s·d^-1和5.0×10^-16d^-1。     

Further Characterization of the Time Transfer Capabilities of Precise Point Positioning (PPP): The Sliding Batch Procedure

In recent years, many national timing laboratories have installed geodetic Global Positioning System receivers together with their traditional GPS/GLONASS Common View receivers and Two Way Satellite Time and Frequency Transfer equipment. Many of these geodetic receivers operate continuously within the International GNSS Service (IGS), and their data are regularly processed by IGS Analysis Centers. From its global network of over 350 stations and its Analysis Centers, the IGS generates precise combined GPS ephemeredes and station and satellite clock time series referred to the IGS Time Scale. A processing method called Precise Point Positioning (PPP) is in use in the geodetic community allowing precise recovery of GPS antenna position, clock phase, and atmospheric delays by taking advantage of these IGS precise products. Previous assessments, carried out at Istituto Nazionale di Ricerca Metrologica (INRiM; formerly IEN) with a PPP implementation developed at Natural Resources Canada (NRCan), showed PPP clock solutions have better stability over short/medium term than GPS CV and GPS P3 methods and significantly reduce the day-boundary discontinuities when used in multi-day continuous processing, allowing time-limited, campaign-style time-transfer experiments. This paper reports on follow-on work performed at INRiM and NRCan to further characterize and develop the PPP method for time transfer applications, using data from some of the National Metrology Institutes. We develop a processing procedure that takes advantage of the improved stability of the phase-connected multiday PPP solutions while allowing the generation of continuous clock time series, more applicable to continuous operation/ monitoring of timing equipment.     

综合多家实验室的原子时标发布系统设计

综合多家实验室的原子时标发布系统,是根据国内8家守时实验室提供的原子钟数据进行模块化设计而完成的。该系统包括原子钟数据预处理,原子时标计算和原子时标数据发布3个模块;采用MATLAB进行数据处理与时标计算,用GUI进行数据可视化设计;具有算法流程清晰,功能模块简洁,人机交互界面友好等特点。实际数据运行结果表明,系统设计的综合原子时标与UTC的时间偏差优于±10ns,数据发布内容可满足国内相关领域科研的需求。     

Consistency of MGEX Orbit and Clock Products

The analysis centers of the Multi-GNSS Pilot Project of the International GNSS Service provide orbit and clock products for the global navigation satellite systems (GNSSs) Global Positioning System (GPS), GLONASS, Galileo, and BeiDou, as well as for the Japanese regional Quasi-Zenith Satellite System (QZSS). Due to improved solar radiation pressure modeling and other more sophisticated models, the consistency of these products has improved in recent years. The current orbit consistency between different analysis centers is on the level of a few centimeters for GPS, around one decimeter for GLONASS and Galileo, a few decimeters for BeiDou-2, and several decimeters for QZSS. The clock consistency is about 2 cm for GPS, 5 cm for GLONASS and Galileo, and 10 cm for BeiDou-2. In terms of carrier phase modeling error for precise point positioning, the various products exhibit consistencies of 2–3 cm for GPS, 6–14 cm for GLONASS, 3–10 cm for Galileo, and 10–17 cm for BeiDou-2.     

Time Transfer by Passive Listening Over a 10-Gb/s Optical Fiber

A technique for time and frequency transfer over an asynchronous fiber optical transmission control protocol (TCP)/IP network is being developed in Sweden by SP Measurement Technology together with STUPI. The technique is based on passive listening to existing data traffic at 10 Gb/s in the network. Since the network is asynchronous, intermediate supporting clocks will be located and compared at each router. We detect, with a specially designed high-speed optoelectronic device, a header recognizer, the frame alignment bytes of the synchronous optical network (SONET)/synchronous digital hierarchy (SDH) protocol, as a reference for the supporting clock comparison. The goal of the project is to establish a time transfer system with an accuracy on the nanosecond level. In this paper, we present the results of a time transfer over a distance of 5 km. We have compared two clocks: a cesium clock at the Swedish National Laboratory for time and frequency and a remote rubidium clock. The results of the time transfer with the fiber link have been simultaneously compared to measurements with a Global Positioning System (GPS) carrier phase link in terms of precision and stability. The root-mean-square (rms) difference between the time difference measured with the fiber link and the GPS link is approximately 300 ps. A large part of the difference is due to the heating of the GPS antenna cable, which introduces daily delay variations on the order of 1 ns from peak to peak. For one of the days with small day-to-day variations in temperature, the corresponding rms difference is 72 ps, and the Allan deviation is below 30 ps for averaging times longer than 5 min.     

Simple Time and Frequency Dissemination Method Using Optical Fiber Network

This paper describes a simple and cost-effective method of frequency dissemination. In current digital communication networks, node clocks are hierarchically synchronized to the atomic master clock through fiber links. This synchronized network is used as an intermediate link for remote calibration services like the global positioning system common-view method. A prototype reference signal generator has been developed for recovering the communication clock signal and synthesizing a 10-MHz signal from it. The generator output frequency at the client site can be traced to coordinated universal time (UTC) National Metrology Institute of Japan (NMIJ) with some uncertainty, depending on the stability of the node clocks and the distance from the master clock. The stability performance of the generated reference signal has been tested at Okinawa-the farthest prefecture from Tokyo, where the master clock is located (baseline distance of 1500 km). The primary rate (1.544 MHz) for telecommunication services was chosen for the 10-MHz signal generation in the experiment. A sinusoidal phase fluctuation within a one-day period is dominantly observed. This fluctuation is mainly caused by fiber expansion and contraction due to normal daily temperature changes. It degrades the stability (Allan deviation) to the level of 5 X 10^-13 (t = 40 000 s, which is almost half a day). However, the major part of the phase fluctuation can be canceled by averaging a full day's data. In this case, the Allan deviation becomes 1 X 10^-13, which is obtained at Okinawa over ten consecutive days of measurement. The worst average frequency offset relative to UTC (NMIJ) (one-day averaging) is -6.3 X 10^-13. The results indicate that this method promises to be suitable for most applications, providing an uncertainty of less than 1 X 10^-12 at an averaging time of one day.     

Accuracy of International Time and Frequency Comparisons via Global Positioning System Satellites in Common-View

Frequency differences between major national timing centers are being resolved with uncertainty of less than 1 part in 1014, using satellites of the Global Positioning System (GPS) in common-view. Portable clock and GPS time differences are in excellent agreement. Around the world GPS measurement between three laboratories had a time residual of 5.1 ns.     

片上波动影响下的Mesh结构时钟系统的性能分析方法

考虑到片上波动对Mesh结构时钟系统的影响,提出了一种基于统计理论的时钟系统性能分析方法。该方法的核心思想是在真实的解析函数难以求解的情况下,采用统计分析方法对该函数进行拟合。从两方面着手研究:如何拟合时钟偏差的概率分布;如何拟合前驱动层时钟路径的时延对时钟偏差的影响。实验证明,时钟偏差的概率分布可用正态分布拟合,而前驱动层时钟路径的时延与时钟偏差的关系可采用多元线性回归模型进行拟合。因此,这套拟合方法使设计人员能够通过正态分布的概率分布函数评估不确定性约束是否合理;在设计后期,根据多元线性回归模型调节优化前驱动层,提高时钟系统的性能。     

Research on Time Keeping at NIM

UTC(NIM), which is developed and maintained by NIM, is the time and frequency primary standard in China. UTC(NIM) is generated originally by a clock ensemble, and is traced to UTC by participating in TAI cooperation with GNSS time and frequency transfer methods. TWSTFT earth station has been established at NIM new campus to join the Europe?CAsia link. In this paper, the new development on the realization of UTC(NIM), the GNSS time and frequency transfer and TWSTFT and our briefly future plan are introduced.