压电谐振传感器机理在超低频振动中的研究

提出了利用压电谐振机理实现超低频振动传感器的实用方法,通过对压电谐振式传感器机理分析研究,得出可测超低频范围可以在0～3Hz.对该超低频振动传感器的具体电路、工作原理以及模拟结果进行了系统的分析与阐述.     

阻抗管中的隔声量测试方法

介绍了在阻抗管中对材料的垂直入射隔声量的测试原理，详细介绍了使用四传感器法测试隔声量的测试方法。分别在两种不同的边界条件下进行不安装样品和安装样品两种状态的测量来对阻抗管非理想吸声末端进行补偿，准确的测得了材料的隔声量。     

一种使用矢量网络分析仪的阻抗测量改进方法

基于反射法理论提出了一种使用矢量网络分析仪测量集总参数元件阻抗的方法,引入阻抗匹配电路,拓宽了矢量网络分析仪的阻抗测量范围.通过对匹配电路二端口网络模型中参量A的分析,给出相应的被测元件的阻抗计算式,消除了夹具对测量结果的影响.采用矢量网络分析仪直接测量法和该阻抗测量法分别测量了5种不同阻值的金属膜电阻,结果表明,该阻抗测量方法的测量精度高于矢量网络分析仪直接测量的精度,可在30 kHz～100 MHz频率范围内实现几欧至千欧阻抗的精确测量.     

Analysis of Modulation Method for Measuring Atomic Resonant Frequency

In microwave spectroscopy and in atomic frequency standards, the atomic resonant frequency is often determied by the use of harmonic frequency modulation of a microwave signal. The effects of line asymmetry and modulating-signal nonlinear distortions are investigated by the use of an analytic approximation of the resonance line by means of an algebraic polynomial. The coefficients of the polynomial are determined experimentally and also derived theoretically. Detailed numerical results for a Ramsey resonance line in a cesium clock are given.     

一种新型的谐振梁频率测量方法研究

谐振梁是一种应用广泛的谐振器。谐振式传感器可以通过测量谐振梁谐振频率的变化,解算谐振梁所受的轴向载荷的大小,从而达到测量目的。目前谐振梁常用的频率测量方法对于动态测量问题的效果并不理想,在很多应用场合都受到限制。本文针对双端固支型谐振梁的频率测量问题,设计了一种基于希尔伯特变换的频率测量方法。使用数值方法对谐振梁振动方程进行求解,获得多种典型的测试信号。仿真实验表明,该方法能很好地获取动态信号频率。     

Digital Method for Determining the Initial Phase of a Harmonic Signal at a Sampling Frequency Less Than the Nyquist Frequency

Measurement Techniques - A digital method is proposed for determining the initial phase of a harmonic signal at a sampling frequency less than the Nyquist frequency. The method includes sampling...     

压电谐振滤波器的高频谐波响应

提出压电谐振滤波器不能很好地滤除高频谐波的问题,结合一个具体例子理论推导了压电谐振滤波器存在许多干扰谐振频率,从而不能有效滤除一些特定频率的干扰信号．为了解决这个问题,提出一种改进型的静电激励谐振滤波器．为了说明其可行性,具体分析了改进型双端固支微梁静电激励谐振滤波器,理论推导证实基于双端固支微梁的各阶振型正交的原理,通过适当调整激振电容的间距,双端固支微梁的高阶振动模态受到很好的抑制,因此这种谐振滤波器可以有效阻止滤波器中心频率的高频谐波的通过．     

确定纳米压入面积函数的改进方法

针对薄膜等微小结构材料力学性能测试面积函数测量问题,提出了一种改善微小压入深度下压头面积函数准确性的方法.该方法将压头与被测样品之间的投影接触面积与压头针尖曲率半径和角度相关联,解决常用的面积函数确定方法在50 nm以下浅压痕测量中不可靠的问题.经实验验证,该面积函数确定方法可以提高微小接触深度下压入硬度和折合模量的测...     

A Method for Determining the Residual Inductance of a Variable Air Capacitor at Radio Frequency

A procedure is outlined which furnishes a method for the measurement of the residual inductances of a standard capacitor and a specimen capacitor which are connected parallel to each other for a substitution measurement. From two junction points connected to a reactance meter, i.e., the high-potential and the earth-potential junction points, the residual inductances of both capacitors, including those of each lead wire, are measured to several percentages at 50 MHz without disconnecting any leads or capacitors or the reactance meter.     

压电加速度传感器Hn估计校准方法

针对压电加速度传感器灵敏度校准过程中噪声对校准结果的影响难以消除的问题,结合Hn估计方法,利用其多次求互相关函数并求平均值的特性对系统噪声进行抑制.用"半长法"进行互相关计算,对多组采样信号进行互相关计算后再用FFT法进行功率谱计算,可得到功率谱的无偏估计.实验结果证明,利用该方法可提高压电加速度传感器灵敏度校准结果的...     

激励功率对微机械谐振梁谐振频率的影响

对谐振式微机械传感器的敏感元件——微机械谐振梁的谐振频率特性进行了详细的实验研究,并从理论上分析了激励功率对谐振频率的影响．实验结果表明,谐振频率随着激励功率的增加而近似线性减小,当激励功率从1．1mW提高到10．1mW时,谐振梁的谐振频率降低了1．609kHz,灵敏度为0．179kHz／mW．实验结论与理论分析的结果基本一致．若要使激励功率对谐振频率的影响减小,则要求降低激励功率并减小梁的长度,增大梁的厚度和宽度．上述研究结论对优化谐振式微机械传感器敏感元件结构尺寸的设计有指导意义．     

Numerical Method of Determining the Characteristics of the Spectral Sensitivity of Television Image Receivers

A new method of determining the characteristics of the spectral sensitivity S() of television image receivers is proposed. The method is based on approximating the spectral sensitivity by a previously known function with unknown parameters. Using a set of wide-beam filters, the response of a television image receiver to the action of radiation from a source with known spectral distribution is measured. From the results obtained, the approximation coefficients are found and the required function S() is recovered.     

The Dynamic Response of a Resonant Frequency Tracking System

A study of a resonant frequency tracking system, to be used in measurement systems where the sensing element is a resonant structure is presented. The tracking system was used to lock an oscillator to the resonant frequency of a cavity operating in the X-band. The resonant frequency of the sensor was assumed to be a function of the quantity being measured. A theoretical analysis of the resonant frequency tracking system was done for both linear and nonlinear operations resulting from the properties of the sensor. A model of the tracking system was designed and an analysis of the system response was performed using computer techniques.     

结构损伤识别中灵敏度法的改进

针对原有灵敏度法对复杂结构损伤识别中存在的不足（误判损伤位置和高估损伤程度），本文对其进行了改进。改进后的方法仅利用结构损伤前后的前两阶模态参数即可确定结构损伤的位置并评估结构损伤的程度。为验证改进后方法的有效性，利用二维钢架结构有限元模型数值模拟了五种典型的损伤工况，用原有灵敏度法和改进后的方法进行了识别。结果表明，与原有灵敏度法相比改进后的方法提高了结构损伤识别的精度，并且该方法简便，有望应用于实际结构中。     

Young's Modulus Measurement of Thin Films by Resonant Frequency Method Using Magnetostrictive Resonator

At present, there are many methods about Young's modulus measurement of thin films, but so far there is no recognized simple, non-destructive and cheaper standard measurement method. Considering thin films with various thicknesses were sputter deposited on the magnetostrictive resonator and monitoring the resonator's first-order longitudinal resonant frequency shift both before and after deposition induced by external magnetic field, an Young's modulus assessing method based on classical laminated plate theory is presented in this paper. Using the measured natural frequencies of Au, Cu, Cr, Al and SiC materials with various thicknesses in the literature, the Young's modulus of the five materials with various thicknesses are calculated by the method in this paper. In comparison with the Young's modulus calculated by the other methods, it is found that the calculated Young's modulus for various thicknesses are in good agreement with the Young's modulus values in the literature. Considering the simple and non-destructive characteristics of this method, which can effectively describe the effect of the thickness on the Young's modulus, it has the potential to become a standard assessing method of thin film Young's modulus.     

铷原子频标中微波谐振腔加载特性的微扰法分析

本文用微扰法分析了铷原子频标中圆柱形谐振腔内紧贴内壁加载一薄玻璃腔泡后对谐振腔谐振频率产生的影响.通过理论推导得到了由玻璃介质引起的谐振频率偏移的解析式,并对TE011模的谐振频率与玻璃厚度、径向长度的关系进行了数值计算与分析,得到了该种谐振腔的谐振频率随介质厚度和径向长度的不同而发生变化的曲线.结果表明,谐振腔加载玻璃腔泡后的谐振频率较空腔时变小,但随着腔壁厚度增大逐渐减小,而随着径向长度增大谐振频率先减小而后增大.以上结论对于微波谐振腔在原子频标中的设计应用有着一定的指导价值.     

压电式高频振动台的研制

根据高频振动基准装置的研究现状和应用需求,研究了压电式高频振动台的优化设计方案,并对压电式高频振动台在设计中的几个重要问题:高频台各组成部分的功能及选择、压电叠堆设计参数的优化、接触界面对振动台性能的影响与预应力的选择及影响等进行了分析。研制了新型压电式高频振动台,其工作频率为2～50 kHz,最大振幅500 nm。给出了新型压电式高频振动台的主要技术指标和比对实验数据。     

A Novel Method for Determining the R-Card Sheet Impedance Using the Transmission Coefficient Measured in Free-Space or Waveguide Systems

Free-space and rectangular waveguide techniques for determining the effective complex permittivity and, ultimately, the effective sheet impedance of an R-card using the forward transmission coefficient are presented. The advantage of using a transmission coefficient method instead of a more traditional reflection-based technique is discussed. The exact transcendental expressions relating the transmission coefficient and effective complex permittivity are derived and approximated using the Maclaurin series for sine and cosine. It is shown that the Maclaurin series expansion leads to simple closed-form solutions to the effective complex permittivity and avoids the use of sensitive and often unstable root search algorithms, which are necessary to solve transcendental equations. The accuracy of the approximations is directly related to the R-card's thickness and wavenumber. Free-space (4–16 GHz) and waveguide (8.2–12.4 GHz) measurements are made using two R-cards of differing thicknesses and impedances to demonstrate the method and regimes of validity. An uncertainty analysis is also performed to demonstrate the robustness of the technique.      

对变频医用超声诊断仪超声源所属档次的判定方法

随着经济和科技的发展,越来越多的医用超声诊断仪超声源的频率呈现变频现象,本文针对出现的新情况,根据医用JJG639-2005《医用超声诊断仪超声源》检定规程,分析如何判定B超的所属档次。