Accurate and low jitter time-interval generators based on phase shifting method

The paper describes two time-interval generators based on the phase shifting method. The first one utilizes the digital clock manager units integrated in a field programmable gate array (FPGA) device and has jitter below 65 ps (rms) over the range of 4 ns-50 ms, while the second one utilizes a separate direct digital synthesizer and has jitter below 15 ps (rms) over the range of 10.2 ns-50 ms. The phase shifting method can be used to design new low-cost and high-precision time-interval generators using the popular FPGA technology.     

基于有载品质因数的低抖动时钟电路研究

抖动作为衡量时钟信号质量的重要指标,对电子系统的性能具有重要意义。数据采集系统要获得良好的信噪比,就必须要有高性能低抖动的时钟信号。本文应用相位噪声与抖动的关系,同时结合相位噪声Leeson模型,研究了时钟信号发生电路的抖动及相位噪声特性,分析了电路有载品质因数QL对抖动的影响,并给出了电路主要器件与抖动关系的显性表达式。以一种100 MHz低抖动时钟信号发生电路为例,进行了理论分析、仿真和实验验证,并将其应用到2.5 GHz采样时钟信号发生电路中进行了对比测试。结果表明,提高电路的有载品质因素QL可以明显改善其抖动及相位噪声特性。     

基于时滞滤波的周期信号跟踪性能优化控制方法

针对周期信号跟踪时普遍存在的相位滞后现象,提出一种基于时滞滤波的周期信号跟踪性能优化控制方法。介绍了这一方法的原理,对控制对象与系统辨识的方法、结果进行了分析,并进行了数值仿真与试验。数值仿真与试验表明,这一方法可以消除周期信号跟踪时的相位误差,提高周期信号的跟踪精度。     

Linear estimation for discrete-time periodic systems with unknown measurement input and missing measurements

This paper considers the estimation problem for periodic systems with unknown measurement input and missing measurements. The missing measurements phenomenon is described by an independent and identically distributed Bernoulli process. The quality of the estimation achieved by an admissible filter is measured by a performance criterion described by the Cesaro limit of the mean square of the deviation between the remote signal and the estimated signal. By employing the minimum variance unbiased estimation technique, the periodic unbiased estimator is obtained, where the estimator gain is designed in terms of the unique periodic solution of a Lyapunov equation together with the periodic stabilizing solution of a Riccati equation. Finally, a numerical example is provided to show the effectiveness of the proposed estimation approach.     

基于类洛伦茨系统的微弱信号检测及其电路实现

基于一种类洛伦茨(Lorenz)混沌系统,利用周期微扰的混沌控制方法,应用于微弱信号的检测。首先,构建一个受控的类Lorenz检测系统,通过调节系统两参数可将混沌系统控制可在所期望的周期轨道内。利用李雅普诺夫(Lyapunov)指数谱及分岔图分析,选择适当的两个参数值,将系统控制在混沌临界状态,当加入混有高斯白噪声的微弱信号时,系统发生相变,由混沌临界状态转变为周期三状态,从而检测出与外加激励信号同频率的微弱正弦信号。此方法不需要利用梅尔尼科夫(Melnikov)方法计算复杂的系统发生相变的激励信号幅值的精确解,实现方法简单易行,MATLAB仿真结果表明该系统可以实现极低的信噪比。在理论和数值分析的基础之上,该文设计了微弱信号检测电路,仿真和实验结果表明,该方法能够有效实现微弱正弦信号的检测。     

钙离子光时标守时技术研究

近年来光学频率标准(光钟)技术快速发展,国际时间频率咨询委员会计划于 2030 年用光钟重新定义“秒”,并提出了 技术路线,光时标的研究也成为时间频率领域的研究热点。 利用钙离子光钟驾驭微波氢钟,开展高精度光时标信号 TS(Ca + )产 生技术研究。 结果表明,钙离子光钟准连续稳定运行率可达 87% ,稳定度达 8×10 -17 / day。 对光钟和氢钟的频率比对测量分别 采用微波频率锁定方案(上转换)和光生超稳微波方案(下转换),上转换方案引入了并放大了噪声,测量数据比氢钟稳定度差, 而下转换方案产生超稳微波,测量数据频率稳定度与氢钟几乎重合,实现了光钟对氢钟的准确测量。 将测量得到的频差数据直 接置入相位微跃计,产生光时标 TS(Ca + ),独立运行的光时标 TS(Ca + )在一个月内与 UTC 偏差保持在 0. 6 ns 以内。 研究成果 为报送秒定义数据和驾驭自由原子时 TAI 提供技术基础,为提升我国光时标守时能力提供了宝贵的技术支持和工程经验。     

水下自主航行器微光照相机驱动系统设计

提出了基于水下自主航行器的EMCCD微光照相机驱动系统设计方法。首先,分析了EMCCD输出噪声的组成,根据暗电流噪声和时钟感生噪声的关系,给出了常规功率驱动的器件选型原则和设计方法;讨论了使用图腾柱电路实现电子倍增驱动的功耗问题,并给出了改进方案;使用高频系统时钟实现了驱动相位和脉宽的微调,解决了驱动时序波形幅度重叠率不足的问题;最后,给出了使用CCD201-20搭建的水下相机结构和实验结果。实验结果表明,系统产生的常规驱动信号频率为时钟频率10 MHz,串行转移时钟的幅度重叠率优于50%,并行转移时钟的幅度重叠率优于90%,驱动信号的相位调整精度为18°,脉宽调整精度为5 ns,驱动波形稳定、平整,电子倍增驱动信号高电平可调,功耗相较于优化前降低7.2%。本文所介绍的EMCCD驱动系统设计方法充分兼顾了驱动系统的噪声、体积和功耗问题,可以广泛应用在水下微光成像乃至常规CCD领域。     

基于Duffing振子检测频率未知微弱信号的新方法

针对现有混沌振子难以检测频率未知微弱信号这一难点,提出利用Duffing振子输出值的方差峰值结合遗传算法检测淹没在强噪声背景中频率未知微弱信号的一种新方法。从分析混沌系统结构参数的阈值入手,讨论了周期策动力的频率、初始相位和噪声对系统运行状态的影响;研究系统输出值方差与系统状态的对应关系,探讨待测信号频率以及与周期策动力之间相位差对状态变量方差和状态转换时间的影响。由此,提出采用具有相位偏移的Duffing振子阵列覆盖全相位,并结合遗传算法,优化求解不同频率输入信号下系统输出值方差的极值,以此得到待测信号频率的方法。该方法解决了现有混沌振子类检测方法必须已知信号频率的限制。实验结果证明了本方法能准确、快速地检测待测信号频率。新方法的状态判定简便、检测精度高、更为灵活、适应性强,为微弱信号的检测提供了新的手段。     

多参数协同调制的高分辨力直线时栅位移传感器

为了解决高精度的直线时栅位移传感器依赖空间超精密刻线和刻线不均匀等问题,提出一种采用多参数协同调制的新型直线时栅位移传感器。该传感器通过在PCB基板上布置阵列的激励线圈和特定形状的感应线圈,通过调制感应的面积和线圈的参数,感应出电行波信号,经过整形后用高频时钟脉冲插补得到位移量。通过仿真分析设计与样机实验,得出实验结果表明,在不改变空间极距的情况下,使得分辨力在信号源头上提高1倍且有±68μm的测量精度。     

基于智能手机TDOA估计的被动声源定位方法与系统实现

被动目标监测广泛应用于国防、安全等领域。针对被动声目标监测,首次提出了基于手机平台的被动式声目标定位方法,并设计和开发了原型系统。针对手机间时钟同步对被动式信号到达时间差精度的影响,采用手机内置的麦克风和扬声器发送和接收同步声信号的方式,从而避免了节点间无线同步到声信号采集间的时间延迟不确定性。为了提高信号发送和接收时刻的估计精度,将时间戳信息调制到设定的线性调频声信号,并采用广义互相关方法来实现信号波形检测。进一步,针对被动目标声源的非合作特性,采用统计判决理论和语音活动性检测相结合的方法对观测信号进行联合检波,获得被动目标声源到达时间的高精度估计,即被动声源到手机间的到达时间差。最后,通过多部手机搭建了原型系统并设计实验,结果表明定位误差不超过10%的概率达到80%。     

基于Wigner分布的齿轮箱振动信号相位估计

时域同步平均是齿轮箱诊断技术的基础,目前这种方法依赖于转速传感器提供相位同步信号。探讨了在没有转速传感器的前提下,由振动信号本身得到相位过零信号的方法。建立了齿轮箱振动信号的一种简化理论模型,通过理论分析得到了一种基于Wigner分布的相位估计方法。将这种方法应用于实际的齿轮箱振动数据,证明这种方法是有效的。     

Note: ultrasonic gas flowmeter based on optimized time-of-flight algorithms

A new digital signal processor based single path ultrasonic gas flowmeter is designed, constructed, and experimentally tested. To achieve high accuracy measurements, an optimized ultrasound driven method of incorporation of the amplitude modulation and the phase modulation of the transmit-receive technique is used to stimulate the transmitter. Based on the regularities among the received envelope zero-crossings, different received signal's signal-to-noise ratio situations are discriminated and optional time-of-flight algorithms are applied to take flow rate calculations. Experimental results from the dry calibration indicate that the designed flowmeter prototype can meet the zero-flow verification test requirements of the American Gas Association Report No. 9. Furthermore, the results derived from the flow calibration prove that the proposed flowmeter prototype can measure flow rate accurately in the practical experiments, and the nominal accuracies after FWME adjustment are lower than 0.8% throughout the calibration range.     

A Vernier Time-Interval Measurer on a PLIC

A vernier time-interval measurer with a computed interpolation coefficient, based on an XCS05XL PLIC from the XILINX company, is described. The resolving power of the measurer is 0.625–0.25 ns with a 20- to 50-interpolation coefficient and a 80-MHz reference signal. The PLIC application makes it possible to decrease the overall dimensions of the measurer without worsening the available accuracy.     

量化误差对周期信号总失真度评价的影响及修正

讨论了量化误差对周期信号失真度测量评价结果的影响,详细阐述了两者之间的关系,并给出了量化误差对周期信号失真度测量造成的影响及其修正关系的数学公式。在正弦波失真度评价中进行的仿真实验结果,验证了本文结论及过程的正确性及切实可行性。     

一种消除周期性毛刺相位误差的互补格雷码双 N 步相移法

互补格雷码双 N 步相移法因其具有鲁棒性好、检测精度高等特点在条纹投影轮廓术领域成为研究热点。 然而,传统互 补格雷码双 N 步相移法存在检测效率低以及未消除周期性毛刺相位误差的问题。 针对这些问题,本文对传统互补格雷码双 N 步相移法进行改进消除周期性毛刺相位误差,首先通过相机捕获形变条纹图像并计算出两组截断相位,然后利用两组截断相位 的相关性消除检测数据中的相位差、周期性毛刺相位误差,再对两组截断相位进行融合,最后通过互补格雷码相位展开法对融 合后的截断相位进行相位展开。 实验得出本文方法在检测效率不变的情况下,能有效消除周期性毛刺相位误差,得到高精度展 开相位,相比于未消除周期性毛刺相位误差的互补格雷码双 N 步相移法,本文检测方法精度提高了约 24. 57% ,相比于互补格 雷码 N 步相移法,本文检测方法精度提高了约 6. 29% 。     

Local phase measurements of light in a one-dimensional photonic crystal

For the first time the local optical phase evolution in and around a small, one-dimensional photonic crystal has been visualized with a heterodyne interferometric photon scanning tunnelling microscope. The measurements show an exponential decay of the optical intensity inside the crystal, which consists of a periodic array of subwavelength air rods fabricated in a conventional ridge waveguide. In addition it is found that the introduction of the air rods has a counterintuitive effect on the phase development inside the structure. The heterodyne detection scheme allows the detection of low-intensity scattered waves. In the vicinity of the scattering air rods phase singularities are found with a topological charge of plus or minus one.     

Review of satellite disciplined clock system

Satellite disciplined clock system (SDCS) composed of satellite timing receiver and local frequency synthesis is widely applied for its high accuracy and low cost.This paper provides a review of SDCS.K...     

Application of Hilbert-Huang Decomposition to Reduce Noise and Characterize for NMR FID Signal of Proton Precession Magnetometer

The parameters in a nuclear magnetic resonance free induction decay (FID) signal contain information that is useful in magnetic field measurement, magnetic resonance sounding and other related applications. A real time sampled FID signal is well modeled as a finite mixture of exponential sequences plus noise. We propose to use the Hilbert-Huang transform (HHT) for noise reduction and characterization, where the generalized Hilbert-Huang represents a way to decompose a signal into so-called intrinsic mode function (IMF) along with a trend, and obtain instantaneous frequency data. First, acquiring the actual untuned FID signal by a developed prototype of proton magnetometer, and then the empirical mode decomposition is performed to decompose the noise and original FID. Finally, the HHT is applied to the obtained IMFs to extract the Hilbert energy spectrum of the signal on the frequency axis. By theory analysis and the testing of an actual FID signal, the results show that, compared with general noise reduction methods such as auto correlation and singular value decomposition, combined with the proposed method can further suppress the interfered signals effectively, and can obtain different components of FID signal, which can be used to identify the magnetic anomaly, the existence of groundwater etc. This is a very important property since it can be exploited to separate the FID signal from noise and to estimate exponential sequence parameters of FID signal.     

A new visualisation and measurement technology for water continuous multiphase flows

This paper reports the performance of a research prototype of a new multiphase flow instrument to non-invasively measure the phase flow rates, with the capability to rapidly image the flow distributions of two- and three-phase (gas and/or oil in water) flows. The research prototype is based on the novel concepts of combining vector Electrical Impedance Tomography (EIT) sensor (for measuring dispersed-phase velocity and fraction) with an electromagnetic flow metre (EMF, for measuring continuous-phase velocity with the EIT input) and a gradiomanometer flow-mixture density metre (FDM), in addition to on-line water conductivity, temperature and absolute pressure measurements. EIT–EMF–FDM data fusion embedded in the research prototype, including online calibration/compensation of conductivity change due to the change of fluids' temperature or ionic concentration, enables the determination of mean concentration, mean velocity and hence the mean flow rate of each individual phase based on the measurement of dispersed-phase distributions and velocity profiles. Results from first flow-loop experiments conducted at Schlumberger Gould Research (SGR) will be described. The performance of the research prototype in flow-rate measurements are evaluated by comparison with the flow-loop references. The results indicate that optimum performance of the research prototype for three-phase flows is confined within the measuring envelope 45–100% Water-in-Liquid Ratio (WLR) and 0–45% Gas Volume Fraction (GVF). Within the scope of this joint research project funded by the UK Engineering & Physical Sciences Research Council (EPSRC), only vertical flows with a conductive continuous liquid phase will be addressed.     

Measurement of heart rate variability and stress evaluation by using microwave reflectometric vital signal sensing

In this paper, we present two robust signal processing techniques for stress evaluation using a microwave reflectometric cardiopulmonary sensing instrument. These techniques enable the heart rate variability (HRV) to be recovered from measurements of body-surface dynamic motion, which is subsequently used for the stress evaluation. Specifically, two novel elements are introduced: one is a reconfiguration of the HRV from the cross-correlation function between a measurement signal and a template signal which is constructed by averaging periodic component over a measurement time. The other is a reconstruction of the HRV from the time variation of the heartbeat frequency; this is evaluated by a repetition of the maximum entropy method. These two signal processing techniques accomplish the reconstruction of the HRV, though they are completely different algorithms. For validations of our model, an experimental setup is presented and several sets of experimental data are analyzed using the two proposed signal processing techniques, which are subsequently used for the stress evaluation. The results presented herein are consistent with electrocardiogram data.