基于FPGA的北斗驯服铷原子频标装置的研制

为了提高铷原子钟频率的准确度和稳定度,设计了基于FPGA技术的多路输出北斗驯服铷原子频标装置。装置采用粗测和细测的时间间隔测量方法实现铷原子频率的驯服和时间跟踪与同步。采用模块化设计和编程,提高了装置的通用性和可移植性。以铯原子钟时间频率为参照,利用该装置对铷原子钟驯服前后的数据进行多次比对测试,结果表明其频率的相对准确度达到了1.5×10^-13,相对稳定度达到6.97×10^-13,与驯服之前相比,铷原子钟频率的准确度和稳定度均得到大幅提高和改善。     

应用于相干布居囚禁原子钟的低相位噪声微波频率综合器

相干布居囚禁(CPT)原子钟作为微波原子钟的一种类型,由于不需要微波谐振腔即可实现微波探询,可极大降低体积和功耗,从而实现芯片级、低功耗的原子钟。CPT原子钟性能指标的主要限制因素之一是微波综合器的相位噪声,为了提升CPT原子钟的性能,研制了一种应用于CPT原子钟的低相位噪声频率综合器。实验结果表明,频率综合器在200Hz处的绝对相位噪声为108dBc/Hz。微波综合器由于Dick效应对原子钟频率稳定度的限制为8.2×10^-14,可以完全满足CPT原子钟的性能指标要求。此频率综合器也可更广泛地用于其它高性能微波原子精密测量系统以及计量标准器。     

环境温度对氢原子钟性能的影响

本文探讨了被动型氢原子钟在宽温度环境下的频率特性,为小型、易搬运、高可靠、环境适应性强、高性能氢原子钟的研制提供了参考.将被动性氢原子钟置于温箱,测量其在不同温度下的开机特性、频率稳定度、频率准确度等参量.本文在10℃~35℃的宽温度范围内进行测试分析,研究了环境温度对氢原子钟开机特性、频率准确度及频率稳定度的影响.对于被动型氢原子钟在恶劣环境下的研制和应用提供可靠的依据和参考,也可为研究其它类型原子钟受温度的影响提供借鉴.     

飞秒激光器脉冲重复频率的锁定技术研究

介绍了光纤飞秒激光器脉冲重复频率锁定技术的应用背景及其原理,并设计了一套可快速实现重频锁定的实验装置,最终将激光器的脉冲重复频率锁定到铷原子钟上,使飞秒激光器的脉冲重复频率获得和原子钟同样的稳定度;通过计数器采集锁定后激光器的脉冲重复频率数据,使用Allan方差给出了稳定度评价,对激光器脉冲重复频率锁定前后的稳定度进行了对比。实验证明,自主设计的实验装置可以实现锁定功能,具有很好的实用价值。     

平面螺旋声阵列近场旋转扫描全息成像研究

针对一平面螺旋阵列在噪声源成像应用,分析了波束形成方法在低频段噪声成像能力的局限性,采用等效源法实现了对低频噪声的全息成像。为提高近程声全息成像性能,本文提出并采用不规则平面阵进行旋转扫描测量,重点研究了无参考传感器条件下对扫描数据的相位处理方法,实现了不同时刻测量数据的相位同步,利用仿真研究验证了该方法的有效性和优越性,并通过实际实验进行验证,对450Hz以下频率噪声的成像能力有显著提高。该方法测试条件要求低,测试结果可靠,相关结论具有参考价值。     

锁相环路对氢原子钟性能影响的实验分析

实验以上海天文台SOHM-4型氢原子钟脉泽信号和新研制的模拟-数字混合型锁相环路为基础,主要分析锁相环路参数对氢原子钟输出信号的短期频率稳定度和单边带相位噪声的影响。针对氢脉泽信号高Q值的特殊性,通过理论分析和实验验证寻求与其相匹配的最佳环路参数。实验结果表明,锁相环路的参数设置直接影响到氢原子钟输出信号的性能;在脉泽信号不变的情况下,改进后的锁相环路和主电子学系统可使氢原子钟的频率稳定度提高至1.7×10^-13/1s, 3.3×10^-14/10s, 9.1×10^-15/100s, 2.9×10^-15/1 000s, 1.4×10^-15/10000s,即较之原有的技术指标,在各取样时间范围内,频率稳定度的测试结果均提高了半个量级。     

宽频段短期频率稳定度测试系统方案设计

采用差拍-多周期测量法进行高精度频率稳定度测量,针对高品质频率源需要进行宽频段短期频率稳定度测试的要求,研制宽频段差拍比较器,根据测试要求,组建的系统实现了微波频率和零头频率点频的频率稳定度测量。采用双平衡肖特基势垒二极管电路进行混频,尽可能的减少有源器件引入的噪声干扰。编制相关测试软件和数据处理软件,大大提高测试精度和测量效率。     

一种低功耗被动型CPT原子钟

介绍了一款新研制的被动型相干布局囚禁(CPT)原子钟样机及其主要性能.样机功耗约为4 W,频率稳定度达到在τ＜8000s范围内优于6×10-11τ-1/2,10 MHz 输出频率在1Hz范围内的相位噪声达到-79.1dBc/Hz .所研制的CPT原子钟具有小型、低功耗的特点.     

地面铷原子钟稳定性和一致性研究

研究了铷原子钟的稳定性和一致性。重点对稳定度的不同表示方法进行了比较,对同一铷原子钟不同寿命时期的稳定性、同一类型多个铷原子钟的稳定性进行了比较,研究了断续工作铷原子钟的频率稳定性、漂移率和一致性。     

基于卫星共视原子钟驯服法的远程时间溯源技术研究

通过建立卫星共视原子钟驯服装置,将本地原子时与国家时间频率基准参考站进行共视比对,实现了铷原子钟的驯服标准差2.19 ns,时间偏差稳定度(1天)小于1×10-9,相对频率偏差-8.42×10-17,频率稳定度(1天)小于2×10-14;铯原子钟的驯服标准差1.5 ns,时间偏差稳定度(1天)小于1×10-9,相对频率...     

Estimating the stability of N clocks with correlations

Estimation of an atomic clock's frequency stability, separate from its reference, is often done using a three-cornered hat procedure. A major requirement for the success of this method is that clocks be uncorrelated. If this requirement is not satisfied, the three-cornered hat procedure can lead to misleading or even negative variance estimates. Others have considered this problem and developed an analysis that allows for the possibility of cross correlation between clocks. We have extended and applied these ideas to obtain mathematically consistent frequency stability estimates on atomic clock data from the U.S. Naval Observatory. In addition, we derived an expression for the clock weights that produce a minimum variance combination of clocks in the presence of correlations.     

一种原子钟组加权的优化策略

原子钟组集成技术广泛应用于计时系统中,以保持原子时标的准确性、稳定性和连续性。相同环境下的原子钟之间可能存在一定的相关性,这在一定程度上限制了原子时标性能。从原子钟组与其协方差矩阵的相关性出发,考察了相同环境因素对原子钟频率特性的影响,基于正则化理论设计了一种原子钟组加权方法。将该方法应用于中国计量科学研究院铯钟组,实验表明有效降低了原子钟组的输出频率不稳定性。     

European two-way satellite time transfer experiments using theINTELSAT (VA-F13) satellite at 307°E

A two-way satellite time and frequency transfer (TWSTFT) experiment performed between six European laboratories is reported. Transfers were made on a regular basis over a period of six months. TWSTFT was demonstrated to be a useful method to compare a relatively large number of atomic clocks internationally, as an alternative to the method of common view of global positioning system (GPS) satellites. The GPS common view time transfer method and TWSTFT method were compared over the same link for a period of 150 days. Three TWSTFT's have been performed simultaneously. Time transfers were performed over periods of up to 8 h, enabling the measurement noise of the TWSTFT system and the stability of the atomic clocks to be examined. Time transfers were made in consecutive successions between clocks at three distant Earth stations. Closing errors of up to approximately 4 ns were observed. The magnitude of these closing errors justified further examination. The uncertainties in the determination of the closing errors have been examined along with their origin, characteristics, and dependence on operating parameters     

基于双光子光谱的光学频率标准

首先概述了双光子跃迁的基本原理,然后介绍了连续光和脉冲光激发双光子跃迁的光学频率标准在实验上的进展,考虑到目前双光子光学频率标准的短期稳定度主要受限于本振,因此发展高功率低频率噪声的激光器用于抑制散粒噪声和互调制噪声是提高双光子光学频率标准短期稳定度的最直接有效的办法。最后介绍了双光子光学频率标准在科学上和工程上的应用。基于双光子直接光梳光谱的氢原子能级间距的测量已经成为测量里德堡常数和质子电荷半径的重要实验技术之一,在量子电动力学的检验中发挥着重要作用。双光子光学频率标准和微腔光梳的结合也为光学原子钟的小型化和集成化提供了新的可能。     

原子钟钟差预测不确定度的建模与分析

钟差预测是原子钟时标产生和原子钟驾驭的关键环节。原子钟作为精准的信号源,其信号由确定信号部分和固有噪声即随机部分组成。氢钟和铯钟主要包含两种噪声,即调频白噪声和调频随机游走噪声,这两种噪声是产生预测不确定度的主要因素。根据原子钟数学模型补充推导出原子钟时差数据预测不确定度的数学表达式,并得出了钟组的最小预测不确定度,分析了钟组的台数对预测不确定度的影响。最后通过数据仿真验证了理论的正确性。     

An AC Josephson Voltage Standard for AC–DC Transfer-Standard Measurements

We describe the traceability chain of length measurements at Centre for Metrology and Accreditation (MIKES) from atomic clocks to the lasers of primary interferometers. Crucial part of the traceability chain, an optical frequency comb generator linking optical frequencies to atomic clocks, is described in detail. The frequency comb generator is used in frequency calibrations of iodine-stabilized lasers, which are operated in compliance with the recommendations of the practical realization of the definition of the meter. Measured absolute frequencies of iodine-stabilized lasers, time records of the measurements, and the respective Allan deviations demonstrate the solid performance of the MIKES laser frequency standards. The results are in good agreement with the recommended values, as well as with the independent characterizations of the measured lasers     

Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin‖lin CPT

We evaluate the influence of 2 types of laser sources with different spectral profiles on the performance of vapor cell atomic clocks based on lin‖lin coherent population trapping (CPT) resonances. We show that a short-term stability of 1 − 2 · 10⁻¹¹τ{−1/2} may be reached in a compact system using a modulated vertical cavity surface-emitting laser. Here the stability is limited by the detection noise level and can be improved up to a factor of 4 by increasing the lock-in detection frequency to several tens of kilohertz, which is not possible in standard double resonance atomic clocks. We compare these results with CPT prepared under the same experimental conditions, using 2 phase-locked extended cavity diode lasers, with which we predict a challenging short-term stability of 1 − 3 · 10⁻¹³τ^−1/2, comparable to the state-of-the-art laser-pumped Rb-clocks.     

气液两相流管道噪声测试

气液两相流管道内气流扰动、气体与液体的扰动产生噪声。利用双通道数据采集器/频谱分析仪对实验管道沿程噪声进行数据采集与处理,得到管道噪声频谱图。改变实验条件,对不同气体流量,不同含液量的管道进行噪声测试。通过对噪声频谱图的数据统计与分析,对管道噪声特性进行总结。通过分析可知,管道噪声检测是确定输气管道是否含液及是否出现液塞的有效方法。     

Phase fluctuations in a heterodyne multistage frequency multiplier

Conclusions The inherent phase instability and error of these multipliers are not inferior (as regards frequency stability) to those found in other methods of frequency multiplication.Multiplication with heterodyning is especially justified in frequency comparison of atomic clocks, where the mutual deviation and output frequency instability are much less than the limiting values permissible for undistorted multiplication. A transistorized multiplier is simple, so one can provide reliability over long periods with continuous comparison.The main component in the phase fluctuations in a multiplier is due to noise in the coupling and transformation circuits, so in principle it is possible to improve the stability further via advances in this part of the device.The input stages are of broad bandwidth and have low temperature coefficients, so one can compare frequencies over periods up to 100 sec without thermostatic control without appreciable loss of accuracy.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 41–43, November, 1972.