A precision transformer used for an audio-frequency power standard

A precision current transformer for the audio-frequency band in which an auxiliary current transformer equalizes the potential along the primary and secondary windings of the main current transformer is discussed. The arrangement results in a dramatic reduction of capacitive leakage current. In this way, a ratio error of less than 10 p.p.m. and phase angle error of less than 10 μrad is achieved at frequencies up to 10000 Hz     

Implementation of the beam reversal technique on compact cesiumclocks: towards an improvement in accuracy

Reports the evaluation of the residual phase difference ▵φ in a short (18 cm) Ramsey cavity by implementing the beam reversal technique in an optically pumped cesium beam clock. ▵φ is measured to be 21 ±1.5 μrad, allowing a more accurate evaluation of the frequency performance of this small cesium clock. Finally, the clock accuracy is equal to 1.1·10^-13     

An algorithm for accurately estimating the harmonic magnitudes and phase shifts of periodic signals with asynchronous sampling

A digital sampling algorithm that uses two high-resolution integrating voltmeters in a master-slave configuration for accurately measuring the harmonic magnitudes and phase angles of two low-noise, low-frequency, arbitrary voltage signals is presented. It is shown that it is possible to measure up to 64 harmonic magnitudes of 60-Hz signals with an uncertainty of less than 13 /spl mu/V/V relative to the fundamental using commercial stable signal generators and high-resolution digital voltmeters. It is also possible to measure the phase shift between the fundamental components of two equally-synthesized 60-Hz signals with about 3.8% total harmonic distortion with an uncertainty of less than 2.5 /spl mu/rad. Even lower uncertainties can be obtained for low-distortion signals. The algorithm was applied to the measurement of the harmonics of periodic arbitrary signals generated by a commercial source. The differences between computed and measured values of harmonic magnitude suggest that stable digitally-synthesized signal generators can be used as calculable standards of harmonic distortion with an accuracy of less than 6 parts in 10/sup 5/ relative to the fundamental.     

VOR信号量值溯源技术研究

基于相位发生器和调频调幅设备建立了甚高频全向信标(VOR)标准信号发生装置,将VOR相位量值溯源至国家相位基准,解决了传统基于直接数字信号合成方法难以实现量值溯源的问题。对VOR标准信号发生装置的不确定度进行了评定,VOR相位扩展不确定度小于±0.020°(k=2),VOR调幅深度不确定度为±0.2%(k=2)。基于该标准信号发生装置可以对商用VOR信号发生和解调设备提供校准。     

Transcutaneous measurement and spectrum analysis of heart wallvibrations

For the noninvasive diagnosis of heart disease based on the acoustic and elastic characteristics of the heart muscle, it is necessary to transcutaneously measure small vibration signals, including components with an amplitude of less than 100 μm, from various parts of the heart wall continuously for periods of more than several heartbeats in a wide frequency range up to 1 kHz. Such measurement, however, has not been realized by any ultrasonic diagnostic methods or systems to date. By introducing the constraint least-square approach, this paper proposes a new method for accurately tracking the movement of the heart wall based on both the phase and magnitude of the demodulated signal to determine the instantaneous position of the object so that the vibration velocity of the moving object can be accurately estimated. By this method, small vibrations of the heart wall with small amplitudes less than 100 μm on the motion resulting from a heartbeat with large amplitude of 10 mm can be successfully detected with sufficient reproducibility in the frequency range up to several hundred Hertz continuously for periods of about 10 heartbeats. The resultant small vibration is analyzed not only in the time domain, but also in the frequency domain. As confirmed by the preliminary experiments herein reported, the new method offers potential for research in acoustical diagnosis of heart disease     

Oscillation-test methodology for low-cost testing of active analogfilters

The oscillation-test strategy is a low cost and robust test method for mixed-signal integrated circuits. Being a vectorless test method, it allows one to eliminate the analog test vector generator. Furthermore, as the oscillation frequency is considered to be digital, it can be precisely analyzed using pure digital circuitry and can be easily interfaced to test techniques dedicated to the digital part of the circuit under test (CUT). This paper describes the design for testability (DFT) of active analog filters based on oscillation-test methodology. Active filters are transformed to oscillators using very simple techniques. The tolerance band of the oscillation frequency is determined by a Monte Carlo analysis taking into account the nominal tolerance of all circuit under test components. Discrete practical realizations and extensive simulations based on CMOS 1.2 μm technology parameters affirm that the test technique presented for active analog filters ensures high fault coverage and requires a negligible area overhead. Finally, the DFT techniques investigated are very suitable for automatic testable filter synthesis and can be easily integrated in the tools dedicated to automatic filter design     

光纤式转镜高速相机同步转速传感器研究

设计了一款光纤转镜式高速相机同步转速传感器;运用单片机(MCU)和复杂可编程逻辑器件(CPLD)结合的方式,提出了一种高精度数字测量方法。MCU与CPLD通过串行外设接口(SPI)通信,MCU向CPLD传输相应的火花基数延时和脉冲宽度;探测信号经过放大、整形后传送到CPLD进行滤波、计数处理,CPLD将测量数据经串口发送给计算机进行实时显示,同时输出同步控制信号。测试数据表明:时间测量相对误差小于±0.2%;成像系统像漂移合成误差约为4.5 mm,像漂移时间约为3 μs,满足实验使用要求。     

Optimization of the internal admittance load of an inductivevoltage divider for low ratio error

The distributed capacitances between the strands of an inductive voltage divider degrade the voltage ratio. A calculation scheme to convert the distributed capacitances into equivalent concentrated capacitances at the taps is given. An optimized connection scheme for the strands is calculated to produce concentrated capacitances which are as equal and as small as possible. Capacitors are added at the taps for optimum equalization. The relative error of the output voltage for a 120-V:10-V divider has been reduced to less than 1×10^-7 in phase and less than 1 μrad in quadrature, at a frequency of 50 Hz     

基于约瑟夫森量子电压的谐波电压测量方法研究

约瑟夫森量子电压目前大多应用于正弦信号的测量,极少有针对谐波信号的研究。对可编程约瑟夫森电压基准应用于谐波检测的可行性进行了研究,实现谐波电压向量子电压过渡。在使用阶梯波交流量子电压进行谐波电压测量时,由于过渡过程和吉布斯现象的存在,部分数据出现较大波动;若将该部分处于过渡过程的数据纳入傅里叶变换,会导致恢复得到的信号幅值和相位失真。针对这一问题,提出了一种新的谐波电压计算方法:加权傅里叶变换。该方法通过将处于过渡过程的数据权重置零的方式,实现了谐波电压的准确测量。实验结果表明,谐波电压幅值和相位测量结果较理想,幅值测量标准差均小于1 μV,相位测量标准差均小于15 μrad。     

生产井储层流量在线监测装置研究

研制了一套生产井储层流量在线监测装置。该装置利用超声多普勒频差测量油、气、水的总流量,采用对环境无安全隐患的双能级X射线测量油、气、水的分相含率,采用电导式传感器实现高含水率情况下含水率的快速测量。在室内三相流实验系统上进行了实验,油、水流量的测量误差均小于±7%,气流量的测量误差小于±14%。     

光纤直流大电流传感器非线性机理及校准技术

非线性误差是干涉型数字闭环光纤电流传感器超大电流测量的主要误差源之一。借助琼斯矩阵方法,推导了光纤1/4波片不理想条件下传感器输出与被测电流的理论关系,确定了1/4波片的方位角和相位延迟误差是造成光纤电流传感器超大电流测量非线性的主要原因之一。仿真结果表明:在5~300kA范围内,方位角误差小于4.53°,相位延迟误差小于9.05°,可保证传感器的测量误差小于0.2%。搭建了光纤直流大电流传感器校准系统,提出了分段线性插值补偿方法校准光纤电流传感器的非线性误差。测试结果表明:非线性补偿后传感器的测量误差由最大的0.6%降低到0.1%以内,证明了非线性补偿方法的有效性。     

Determination of the transition frequency of a bipolar transistorusing optoelectronic current sources

The principle is described of a measurement by a method of comparison which allows the transition frequency f_T of a bipolar transistor to be measured. The AC test signal is obtained by optoelectronic injection. The same sine-modulated monochromatic light is shone successively on two photodiodes. The transistor does not need an actual excitation current at the input or short-circuit at the output since a method of comparison is used. The frequency response of the two photoelectric signals approximates a first-order low-pass function. Optoelectronic injection allows the presence of any parasite synchronous induced signals to be detected, leading to more accurate measurements. For a signal-to-induction ratio of 40 dB and a signal-to-noise ratio of 50 dB, the accuracy over the determinations of f_T is about ±5% for both amplitude and phase shift measurement     

交流电压源毫伏级量值准确测量的技术研究

基于电压比例和交直流转换技术,提出了一种对交流电压源的毫伏级量值进行准确测量的方法。采用自行研制的二进制级联结构电压比例装置和792A交直流转换标准,将被测交流电压源的毫伏级量值溯源至交流电压国家基准。实验采用替代测量法,通过选用不同电压比例和不同792A量程的组合,在55Hz~5kHz频率范围内,对1台5720A多功能校准源10~200mV范围的交流电压进行准确测量。结果表明,各毫伏级交流电压示值相对误差的绝对值均不超过±40μV/V,测量结果扩展不确定度优于80μV/V,满足交流电压源毫伏级量值溯源需求。     

移相干涉仪环境微扰的外差检测及信号处理

对环境微振动干扰进行补偿可减小移相干涉测量的误差,其中振动量的检测是实现振动补偿的前提。以声光调制器作为光学移频器,在移相式平面干涉仪中组合成外差干涉测振系统,可以实现光程差微小变化(范围为0到1/2波长)的实时检测。在外差信号处理中采用单片RF/IF相位测量芯片直接对两路40MHz模拟信号进行比相,简化了通常使用的数字测相方法,其精确测相的典型非线性值小于1度。用该系统实际测量了周期性振动和地面冲击振动对干涉仪的影响,获得了干涉仪所受微振动的幅度和相位。     

计量型紫外显微镜微纳米线宽测量技术的研究

计量型紫外显微镜微纳米线宽测量技术是利用光电倍增管的光电转换效应,将线宽的光学信号转换为电信号,并利用后续信号采样处理电路,提取出线宽的轮廓信号。利用激光干涉仪等精密定位装置,搭建了一套线宽测量系统,对线宽标称值为3 μm的标准样板进行测量,得到的线宽测量值为3.025 μm,与标称值仅相差25 nm。实验表明:该方法可以准确地获取线宽的边界信号,实现线宽的准确测量。     

数字示波器大触发延迟时间的校准方法

针对数字示波器的大触发延迟时间,提出了一种标称校准方法。使用正弦激励信号周期作为测量尺度标准,将大触发延迟时间表述成整数个正弦周期与一个小数个正弦周期的合成。小数周期部分用相位差法直接测量获得,而整数部分则通过最大允许误差极限已知的标称大触发延迟时间计算获得,最终将两部分时间合成,得大触发延迟时间测量结果。在数字示波器上所作的一组实验验证了本文方法的正确性与可行性。该方法可用于数字示波器大触发延迟时间的精确测量和计量校准。     

基于小波滤波器组的涡街流量计信号处理方法

涡街流量计应用比较广泛,但是,由于易受管道振动和流场不稳定等因素干扰,如何从强噪声背景下检测出涡街信号频率,一直是个难题.研究了多相结构ⅡR小波滤波器组的设计方法,给出了Butterworth型小波滤波器组的实现方案,将基于小波滤波器组的信号处理方法应用于涡街流量计,并给出最佳频带的判别准则.仿真结果表明,Butterworth型小波滤波器组具有较好的幅频特性和较高的频率精度.     

An Octave-Band Microwave Phase Comparator

A simple apparatus for measuring the relative phase difference between two signals of identical frequency anywhere within an octave band at microwave frequencies is described. Instantaneous measurements can be performed upon carriers that are periodically 100 percent modulated by narrow pulses since no mechanical contrivances are required. Phase information is converted by detectors into four channels of amplitude information, and these are then combined to yield a relative phase measurement that is unambiguous over a 360° range. In principle, the method is independent of relative signal amplitudes, but in practice it is limited by the useful range of the detectors. Two power dividers, a 90° coupler and a 180° hybrid, four detectors, and an oscilloscope comprise the necessary basic hardware. A derivation of the basic principles of the phase comparator is presented, together with a discussion of calibration test results, for every 10° in phase at each of nine separate frequencies over an octave band. Finally, a processing device for generating a digital indication of relative phase angle is also described.     

采用数字相关法测量相位差

本提出了一种用数字相关法测量相关位的方法,并加以详细讨论了和误差分析。本方法具有精度高,抗干扰能力强,硬件少,适用于低频测量等特点。     

A novel technique for testing pulsed RF MSK data communicationdevices

The paper discusses a novel technique for testing Minimum Shift Keying (MSK) impulsive radio-frequency (RF) signal transmitters. This technique utilizes the acquired samples of a single shot signal to determine the trajectories of the frequency and phase, by means of a time domain analysis. The theoretical foundation of this technique is given, discussing the application to a pulsed RF MSK signal modulated with a bit-rate of 5 Mb/s, having a total duration of 6 μs and whose central frequency falls in the band going from 960 to 1206 MHz. The performance of the measurement algorithm (robustness, influence of the digitizer resolution, time base jitter, and noise on the precision of the measurement) has been evaluated by means of simulation tests. The method has been experimentally verified for the characterization of identification friend or foe (IFF) time division multiple access (TDMA) actual devices