共查询到19条相似文献,搜索用时 312 毫秒
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激光二极管自混合干涉信号的频率与外腔振动的速率成正比,为了从自混合干涉信号重建振动信号,采用频率电压变换的方法.用整形后的自混合干涉信号驱动模拟开关,来开关电容做电荷转移实现频率电压变换,用振动的激励信号驱动另一个模拟开关让电容的充电电源随振动的相位变化做极性变换,这样从自混合干涉信号中还原出振动信号.还原出来的信号的振幅与振动的振幅成正比,波形与正弦激励信号的波形一致.该方案操作简便、成本低廉,可以用于有确定激振方式的振动特性测量. 相似文献
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针对转子系统局部碰摩故障特征及声音振动信号特点,采用一种基于声振信号经验模式分解(Empirical Mode Decomposition简称EMD)的轻微局部碰摩故障诊断方法对滑动轴承碰摩故障进行特征提取。由于EMD分解不需要固定的基函数,根据信号特征自适应的调整,从而实现碰摩特征及旋转激励背景信号自动分解。通过设计滑动轴承缺油工况轴承碰摩试验,并进行振动全息测试分析,将所得声振信号本征模式函数时域特征和边界谱特征与转子径向位移及轴承座加速度信号对比分析,确定了碰摩部件;从而证明基于声振信号EMD分解的碰摩故障诊断方法的有效性。 相似文献
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摘 要:构建了钻柱内一维低频纵波传输的有限差分模型,时域和频域仿真分析了换能器位置和载波信号对周期性管结构信道内声传输信号的影响规律,设计了时延脉冲OOK信号调制方法。采用窄脉冲调制信号激励方式,沿管轴方向对有限长模拟钻柱施加纵向激励,进行了测试信号的声传输实验。结果表明,在1W激振功率、77bit/s传输速率和长6.44m模拟钻柱信道的传输条件下,该方法可实现实验室内测试信号的低频声波传输与信号检测,为井下参数的钻柱声遥测系统设计提供理论与试验基础。 相似文献
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应用随机最优控制理论设计桅杆抗风TMD 总被引:2,自引:2,他引:0
桅杆结构风振控制是一个被工程界普遍关心的问题。本文提出采用最小误差激励计算桅杆抗风TMD的设计思想。通过实例分析,对两种分析方案进行比较,证实采用这种基于随机最优控制理论的分析方法,使桅杆结构抗风性能获得理想最优控制的效果。 相似文献
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基于里德堡原子的微波量子精密测量技术由于其高灵敏度、高分辨、宽带宽且可直接溯源至基本物理常数等优势,已在微波量子计量、通信、成像等领域展现出广阔的应用前景。通过提出一种基于里德堡原子的微波相移测量方法,利用热里德堡原子光谱实现对本振(LO)微波场与待测(SIG)微波场的外差探测,得到了相移与待测微波场相移相同的中频(IF)探测信号;然后利用锁相放大算法对探测信号进行处理,得到探测信号相对同频参考信号的相位差;最后,利用位移台在待测微波信号中引入相移,比较位移前后的相位差测量结果,实现了6.92 GHz微波信号相移的测量。对相移测量结果进行线性拟合,得到该频率的微波传播常数,与理论计算结果的相对误差约为0.2%,验证了这种全光学微波相移测量方法的可行性,并为微波量子精密测量技术在通信雷达等领域的应用奠定了基础。 相似文献
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针对卫星通信中射频载波信号光学传输问题,建立了星间微波光子链路,利用两个并联双电极马赫-曾德尔电光调制器,以光载波抑制调制方式实现了星间微波信号的光域传输和下变频。利用贝赛尔函数展开推导了多载波输入情况下接收信号任意谐波和交调分量表达式,得到了输出信号噪声失真比与输入载波数关系,利用曲面投影法求得了不同载波数时电光调制器最佳调制系数,分析了载波数对最佳调制系数、光发射功率和最优信号噪声失真比的影响。结果表明,射频本振调制器的最佳调制系数在载波数变化时可以保持不变,射频信号调制器的最佳调制系数和最优信号噪声失真比随载波数增大而减小,光发射功率随载波数增大而增大。 相似文献
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Bourgeois PY Kersalé Y Bazin N Chaubet M Giordano V 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2004,51(10):1232-1239
In this paper, we describe the implementation of a microwave cryogenic sapphire oscillator (CSO) at the Laboratoire de Physique et Métrologie des Oscillateurs. In our realization we solved the problem of the spurious modes by operating the sapphire resonator in an open cavity. The CSO compared to a hydrogen maser demonstrates a frequency stability better than 3 x 10(-14) at short term. Its long-term frequency instability of the order of 3 x 10(-12)/day is limited by a random walk process. A first attempt to use this reference oscillator to characterize other signal sources is presented. 相似文献
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《IEEE transactions on instrumentation and measurement》1980,29(4):311-315
Experimental verification of the effect of thermal noise on the oscillation amplitude of a maser is described. Two different masers are considered, the H maser with an homogeneous atomic line and the Rb maser with an inhomogeneous line. The effect is characterized by the spectral density of the relative amplitude fluctuations and this parameter is measured with a conventional superheterodyne AM receiver for various maser saturation factors. Experimental results show good agreement with theoretical predicted values. At high saturation factors, a peak appears with a maximum at a frequency close to the Rabi frequency. Observed values at high Fourier frequencies allow a measurement of the atomic power by the knowledge of the absolute temperature of the cavity and the prediction of the oscillator short-term frequency stability. Furthermore, the effect on amplitude and on frequency noise of an external feedback loop used to increase the cavity quality factor is discussed. 相似文献
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《IEEE transactions on instrumentation and measurement》1973,22(4):367-375
The automatic tuning of frequency standards gives a method of removing drifts due to cavity pulling. The paper describes an apparatus designed primarily for tuning the hydrogen maser. The apparatus can also be used for tuning other masers such as the rubidium maser. The system incorporates several of the best features of similar devices previously described in the literature. It includes a digital averager which makes possible the use of a reference oscillator less stable than the maser to be tuned. It includes also a digital integrator, solving the usual problem of offsets in standard integrators. Frequency corrections are made either proportionally or by unit steps through a varactor coupled to the maser cavity. The electronics are made almost entirely with TTL digital integrated circuits (type 7400) for low cost, reliability, and availability. Results on the tuning of rubidium and hydrogen masers are given. 相似文献
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《IEEE transactions on instrumentation and measurement》1983,32(3):410-413
In this paper, we report the results of an experimental study of the short-and mid-term frequency stability for both a hydrogen maser and a rubidium maser operated with an external feedback loop to modify the cavity quality factor. A revised version of the theoretical expression of the frequency stability for this type of maser is given and a numerical solution for various maser parameters is calculated. The predicted frequency stability exhibits an optimum when the cavity Q is varied. The experimental results presented in this study agree with this conclusion. 相似文献
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B. A. Gaigerov G. A. Elkin L. P. Elkina N. D. Zhestkova G. P. Kurnikov B. P. Popov 《Measurement Techniques》1972,15(11):1640-1643
Conclusions The main factors limiting the frequency stability of a hydrogen maser over long periods are magnetic field drift, error in the compensation setting, and inconstancy in bulb temperature. Future researches will be directed to raising the long term stability with continuous operation. We have developed a hydrogen maser with automatic magnetic field stabilization, with an improved frequency modulator that introduces very little Q change, and with a thermostatic cavity. In six months of preliminary tests the systematic frequency drift has been zero from day to day within 10–13. Atomic clocks of this type may be recommended as working time reference standards.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 29–32, November, 1972. 相似文献
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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。 相似文献
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Prestage J.D. Tjoelker R.L. Wang R.T. Dick G.J. Maleki L. 《IEEE transactions on instrumentation and measurement》1993,42(2):200-205
The frequency stability of an atomic standard based on 199 Hg+ ions confined in a hybrid RF/DC linear trap is described. The 40.5-GHz clock transition has been measured to be 17 mHz wide, representing a quality factor greater than 2×1012. A 160-mHz line is used to steer the output of a 5-MHz crystal oscillator to obtain a stability of 2×10-15 for 24000-s averaging times. In a separate measurement, a 37-mHz line is used to steer the output of the superconducting cavity maser oscillator to reach 1×10-15 stability at 10000 s 相似文献
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Koga Y McNeilage C Searls JH Ohshima S 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(1):1-5
A low noise and highly stable microwave exciter system has been built for Cs atomic frequency standards using a tunable sapphire-loaded cavity oscillator (SLCO), which works at room temperature. This paper discusses the successful implementation of a control system for locking the SLCO to a long-term reference signal and reports an upper limit of the achieved frequency tracking error 6×10-15 at τ=1 s 相似文献