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星载原子钟性能的研究对于卫星钟差估计与预报、卫星导航系统的建设与维护等具有重要的意义。采用了德国地学研究中心(GFZ)2021-01-01—2021-12-31多星定轨联合解算的精密钟差产品,基于预处理后的钟差数据,对2021年北斗三号卫星导航系统(BDS-3)星载钟的相位、频率跳变情况进行了统计,探讨了中圆地球轨道(Medium Erth Obit, MEO)卫星铷钟与氢钟的相位、频率序列图特点。使用二次多项式模型分析了BDS-3不同轨道、不同星钟类型卫星钟的频率漂移率和模型噪声等指标的变化规律,基于哈达玛方差从不同时间尺度对BDS-3卫星钟的频率稳定度展开了分析。结果表明,BDS-3卫星钟相位和频率变化相对连续且稳定,其中仅地球静止轨道(Geostationary Orbit, GEO)卫星星钟存在调相行为,MEO卫星和GEO卫星都存在调频行为,且铷钟的调频次数明显多于氢钟。从频漂和模型噪声水平来看,MEO卫星优于其他轨道类型卫星,同铷钟相比,氢钟性能更优。BDS-3星载原子钟的稳定度保持在10-15~10-14量级,MEO卫星星载钟的稳... 相似文献
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导航卫星星载原子钟的在轨性能直接影响导航系统定位、导航与授时(Position, Navigation and Timing, PNT)服务的精度和稳定性。基于武汉大学MGEX分析中心发布的精密卫星钟差产品,对BDS-3卫星星载原子钟的频率稳定性、钟差预报精度和钟速变化特征开展了分析评估。对GPS III和Galileo FOC卫星的星载原子钟性能开展分析,并与BDS-3的星载原子钟性能进行了对比。结果表明,BDS-3 PHM的平均天稳定度为4.62×10-15, 7 d钟差预报精度为2.3 ns, 10 d钟率变化为1.79×10-14 s/s,其长期性能优于GPS III和Galileo FOC星载原子钟。值得指出的是,BDS-3 C19 RAFS的在轨性能远优于其他BDS-3 RAFS。 相似文献
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《无线电工程》2018,(1):46-49
大型通信、测量电子系统一般配备2台或2台以上原子钟作为系统的时间、频率基准,互为备份构建主、备时频信号基准,以提高系统时频信号可靠性,保障系统连续运行。主备原子钟间虽然可通过相位比对、数据分析检测到原子钟工作状态异常状况,但是由于缺乏参考,难以通过时频系统本身区分故障来源,存在故障定位难的技术难点。针对这一问题,提出了一种基于中间振荡器的主、备用原子钟频率跳变检测、短期稳定度分析评估方法,为时频系统主、备用原子钟故障定位提供技术手段,提高时频系统故障判断准确性,并缩减系统故障定位、故障恢复时间。使用3台铷原子钟进行了测试验证,实验结果表明,该方法可实现时钟稳定度的评估,并可实现时钟频率跳变的故障定位。 相似文献
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文中根据小波变换的奇异性检测原理,分析了环境温度变化对原子钟特性的影响。基于小波变换的信号重建原理,将温度变化引起原子钟相位-时间起伏进行时-频域分离。用小波变换理论分析了由于昼夜温度变化引起原子钟周期性波动的原因,结合传统的港分析方法,认证了原子钟相位-时间起伏的周期性。结果表明:在有环境温度调节的环境中,氢原子钟的相位-时间起伏标准差41ns左右,在一般环境中,她原子钟的相位一时间起伏标准差21us左右。改善环境条件可以提高原子钟的频率稳定度。 相似文献
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Peter Daly Ian D. Kitching David W. Allan Trudi K. Peppler 《International Journal of Satellite Communications and Networking》1991,9(1):11-22
The frequency stability and reliability of the clocks are critical to the success of the GPS and GLONASS programs. We will show some of the similarities and differences between the clocks involved in these two systems. Because both systems plan to be operational in the next few years, the data leading up to this operational stage is of significant interest. On-board clocks and the stability of the master control clocks for these systems are analysed. We will discuss the attributes of these two systems as time and frequency references. Their relationship to UTC will also be illustrated. More data over a longer period of time was available for the authors from GPS than from GLONASS. Even so it is obvious that both systems have matured. Though the GLONASS system was developed later, its overall clock performance has improved more rapidly. Some of the more recent GLONASS clock performance is at about the same level as that of the GPS clocks. The analysis has yielded some very interesting contrasts, comparisons and changes in these systems that should be of great interest for time and frequency users, as well as for clock vendors and receiver vendors. 相似文献
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Time/frequency technology provides a reliable aircraft collision avoidance system (CAS) that can operate in either synchronous or asynchronous modes. Precision time-ordered techniques of CAS provide both range and range-rate measurements in a one-way sense to all aircraft as well as ground stations within range of transmitted microwave signals. The cooperative system utilizes exact frequency references coupled with precise synchronization: control of frequency to 1 part in 108and time to less than 1 µs. In addition to performing specific functions of protecting aircraft, the time/frequency CAS provides a means for wide dissemination of submicrosecond timing. Flying clocks, which are an integral part of the airborne CAS, have been providing transcontinental and intercontinental transfer of time since 1964. CAS ground stations can serve as depositories of time and frequency derived from flying clocks, satellites, Loran-C and Omega navigation systems, or television transfer referenced to national and international time/frequency standards. Airborne relay of CAS time provides a ready means for local transfer of time to users that are not within line of sight to a ground station. Thus time and frequency can be disseminated for applications other than collision avoidance. In the process of developing the technology and originating CAS, new systems for communication, position determination, navigation, and vehicle surveillance evolved. Such systems can be structured to operate at high data rates, provide improved accuracy and use less RF spectrum than existing techniques. 相似文献
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This paper considers the problem of estimating the offset in timing of like events at geographically separated locations as a basis for establishing common knowledge of time and, hence, system synchronism. Configurations discussed involve interrogation and reply between a user and a single donor, and one-way propagation between a user and the multiple sites of a reference system. The latter category includes navigation systems, which are shown to be appropriate means for disseminating time. Further ramifications of time dissemination are discussed, including the characteristics of clocks suitable for airborne application. Variables and their relationship and solution are defined for stationary and moving users, and for users of atomic and crystal clocks. For the case in which frequency is offset between clocks, as is likely when crystal oscillators are used, methods are described that permit the estimate of offset in frequency as well as in time. Recursive minimum-variance methods are examined in some detail, and a parametric analysis of performance relative to random and systematic sources of error is given. 相似文献
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Stable Photonic Links for Frequency and Time Transfer in the Deep-Space Network and Antenna Arrays 总被引:1,自引:0,他引:1
Calhoun M. Shouhua Huang Tjoelker R.L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2007,95(10):1931-1946
For more than two decades, NASA deep space network (DSN) frequency and timing metrology has been a driving application for remote transfer of stable radio-frequency signals over fiber-optic cables. Precise, accurate, and stable signals are essential for deep-space communication and tracking, and syntonized and synchronized reference signals from atomic clocks calibrated to coordinated universal time must often be distributed over large distances. Fiber-optic technologies developed at the jet propulsion laboratory have resulted in several operational signal transport capabilities that enable precise spacecraft navigation and sensitive radio science experiments. These techniques are now finding further applicability in metrology applications to remotely compare ultra stable microwave and optical atomic clocks and for antenna array X- and Ka-band signal transport applications where temporal phase stability and alignment are critical. The pioneering DSN photonic link developments and capabilities are summarized, and a stabilized multiphotonic link architecture for ultrastable signal transport in antenna arrays is described. 相似文献
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Sullivan D.B. Levine J. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(7):906-914
The authors present a broad overview of time and frequency technology, particularly those trends relating to the generation and distribution of time and frequency signals. The authors provide a general look at these trends. They refer the reader to other papers, particularly to those in this issue, for greater detail. The topics considered are: background, including accuracy and stability, frequency standards, time transfer systems, and network synchronization; time generation, including various types of atomic clocks and quartz oscillators; and time distribution, including applications of time transfer concepts and practical synchronization limits. The characterization of components and systems is also addressed 相似文献
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在城市峡谷等遮挡环境下,接收机无法连续进行定位解算;并且高程定位精度不能满足用户在立交桥或者盘山公路等环境下的定位需求。在接收机内使用原子钟,可以利用原子钟的高稳定性,对钟差进行高精度的预测。并通过与气压测高仪共同辅助北斗系统定位,可以有效提高接收机的定位精度和连续性;该文首先理论分析了原子钟和气压测高仪辅助定位算法;然后,提出一种气压测高仪初始化校正方法,并通过对钟差噪声类型的分析确定了钟差预测方法;最后,模拟遮挡环境,进行原子钟和气压测高仪辅助北斗卫星导航系统定位试验,并分析了定位结果。结果表明:仅跟踪两颗可见卫星,便可以进行定位解算,并且垂直方向上的定位误差从8.2 m (RMSE)下降到了5.2 m,定位结果的波动从4.6 m下降到了0.8 m。 相似文献
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This paper discusses the role of time and frequency in three areas: 2) the operational Navy Navigation Satellite System, NNSS; 2) an experimental low-altitude navigation concept termed TIMATION; 3) proposals for advanced navigation satellites. These operating, experimental, and proposed systems all use concepts which allow the user to remain passive. The operational NNSS system uses the Doppler technique to establish user positions to ~100 m. In this concept, the frequencies received from the satellite are compared to the frequencies generated in the user equipment. One can also compare the time a signal arrives from a satellite clock to a time generated in the user equipment clock for passive ranging. The paper shows that this passive ranging problem is easily transformed to the celestial navigation problem. Extension of these techniques allows one to use satellites as clock transporters and hence to compare clocks located throughout the globe to 0.5 µs. Experimental results are shown. It has been possible to determine the effects of radiation on quartz crystals and to determine that this effect is due principally to protons. System concepts are described which show this clock/time technique can determine user position, velocity, and time continuously, accurately, and globally. 相似文献
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对于高分辨率星载P 波段SAR 系统,电离层效应对P 波段SAR 会带来一系列较为严重的误差,这些误差与电波频率和电离层积分电子总量(TEC)值关系密切,并使得图像质量下降。为了获得高质量的图像,必须对电离层误差进行校正。该文基于电离层导致的匹配滤波失配的数学模型,指出获得准确的电离层TEC 是校正的关键,提出了一种高精度的基于SAR 回波相位反演电离层TEC 的测量方法,并利用地基P 波段雷达对空间目标进行穿透电离层步进频ISAR 观测验证,实测数据处理结果表明,该方法有效提高了电离层TEC 测量精度,改善了ISAR成像质量,可适于低频段星载SAR 系统的电离层效应测量与校正应用。 相似文献