光纤水听器时分复用阵列串扰分析

采用高相干窄带光源的光纤水听器时分复用(TDM)阵列中,信号光与其余通道的泄漏光之间不是简单的强度叠加,而是互相干涉。以此为基础,推导了8路TDM阵列中各通道光束相互作用的理论公式,得到了光开关的消光比是决定系统串扰的主要因素,最大串扰值约为消光比的一半的结论。信号解调采用相位载波解调(PGC),由于串扰频率分布广且远高于信号频率,提出了采样前先低通滤波的信号检测方案,该方案可滤除串扰高频成分,大大减小串扰频率混叠对PGC解调的影响。     

光纤水听器时分复用检测电路带宽与串扰分析

在光纤水听器时分复用系统中,需要设计高增益,大带宽的信号检测电路.为了减小系统的噪声同时抑制通道问串扰,必须选择合适的电路带宽.本文分析了待检测信号带宽与脉冲形状的关系,以及电路串扰率与电路带宽,脉冲宽度、通道问延时的关系,给出了电路串扰率的解析表达式,得到了电路串扰带来的解调信号误差的表达式,分析表明电路串扰导致的解调信号误差的幅度与电路串扰率成正比,与前一通道施加的声信号的幅度的贝塞尔函数成正比,最后给出了与理论分析相符的实验结果.     

n阶信道传输矩阵特征值分解的串扰抵消研究

为了减小高速互连下串扰对信号传输的影响,进行串扰抵消研究。针对一组n(n3)条耦合微带线间的串扰问题,提出了4阶和5阶耦合微带线信道传输矩阵的简化形式,并在对其进行特征值分解后构建了串扰抵消电路,此电路可以有效改善信号眼图的质量。仿真结果显示,该方法在n=4和n=5条耦合微带线串扰抵消时效果良好。综合n=2和n=3时的仿真,结果表明,此方法可以推广应用到一组n(n≥2)条耦合微带线串扰抵消中。     

一种消除AFM中悬臂梁横向扭转串扰误差的修正技术

串扰效应始终存在于原子力显微镜(AFM)的测量过程中,并影响其测量精度.在对串扰效应的产生机理进行分析,并建立了悬臂梁形变与光斑位置检测器(PSPD)输出信号之间的数学关系的基础上,提出了一种可消除横向扭转串扰影响的修正方法.在该方法中AFM系统可由输出信号直接获得悬臂梁的实际形变量,进而获得原子间作用力的实际值,并通过保持作用力的恒定对样品进行测量.该方法可有效地将悬臂梁扭转导致的纵向信号的变化从系统测得的纵向信号中剔除出去.仿真结果表明,在恒力接触模式下,串扰效应严重影响测量结果,导致测量误差,且针尖.样品夹角导致的串扰效应比摩擦力导致的串扰效应更严重.为验证本文方法消除串扰效应的效果,在应用该修正方法前后分别对标准梯形样品进行测量.实验对比结果表明,在普通恒力接触模式下的样品表面最大测量误差范围为21.2 nm～32.0 nm;对串扰效应进行修正后,最大测量误差范围降低至5.5 nm～10.2 nm.这表明该方法可有效降低AFM中串扰效应导致的测量误差,提高其测量精度.     

超高层建筑顺风向加速度的干扰效应研究

通过刚性模型同步测压风洞试验,获得了各种干扰工况下受扰超高层建筑表面风荷载,并对不同折减风速下的超高层建筑顶部顺风向加速度响应进行计算,详细研究了不同截面宽度、不同高度施扰建筑干扰下受扰建筑顶部顺风向加速度干扰因子包络值的分布规律以及涡激共振干扰机理,并进一步分析了不同截面宽度、不同高度建筑施扰下的干扰因子包络值之间的相关特性。结果表明,由于涡激共振的影响,宽度比为0.4及0.6时的最大干扰因子包络值分别达到2.3和2.06,在工程结构抗风设计中需重点关注高度相仿但截面相对较小的施扰建筑的潜在干扰影响。在非共振情况下,随着宽度比（施扰建筑与受扰建筑截面宽度之比）的增大,放大干扰效应显著的区域越来越大,相应的最大的干扰因子包络值也呈增大趋势。高度比（施扰建筑与受扰建筑高度之比）为1.2和1.0时的干扰因子包络值之间的相关系数达到91%,当施扰建筑高度达到受扰建筑的1.2倍后,包络干扰因子的分布基本不变。     

光镊力谱系统双光束串扰因素研究

为了降低和消除光镊力谱系统中双光阱之间的干扰,进一步提高测试精度,本文对双光阱光镊系统中两光束间串扰的成因及其对力谱测量的影响展开了研究.研究发现,高倍物镜组与样品池构成的光学结构会引起光束偏振态的改变,是双光束串扰形成的主要因素;偏振分光棱镜自身的分光特性是串扰产生的另一因素;光阱捕获的微球,虽然改变了光束的形状和传播方向,但在光束串扰方面贡献很小.双光束的串扰信号叠加在探测的光强信号上,影响了光阱刚度和位移灵敏度的标定,最终导致力学测量的偏差.光镊系统中双光束的串扰量在同一次实验的一定时间内基本稳定.根据双光阱光镊系统的这一特点,本文提出了实时测量双光阱光镊系统两光阱独立存在时和同时存在时双光阱的刚度和位移灵敏度的方法,并经多次实验求平均后得到两种情况下双光阱的刚度和位移灵敏度的比值,在后续实验中,将该比值作为修正参数对实测的力谱曲线进行修正.结果表明,该方法有助于减小双光束串扰的影响,优化力谱测量结果,测试精度提高3.4!.     

三线系统的串扰分析与仿真

概要介绍了高速电路设计中的串扰和耦合机理。借助Mentor Graphics公司的信号完整性分析工具HyperLynx仿真软件，对PCB板中造成信号串扰的多种因素进行分析。为了使串扰达到最大化，更接近实际，采用了三线系统对串扰进行了全面的分析。最后根据仿真结果，提出了减小串扰的有效措施。     

数据采集系统通道间串扰的校准方法

介绍通道间串扰的成因和JJF 1048-1995《数据采集系统校准规范》中关于直流信号对直流通道的串扰能力的校准方法,并提议在一定工况条件下还应对交流信号对直流通道的串扰能力以及交流信号对交流通道的串扰能力进行校准,最后通过实验对上述三种串扰进行计算和不确定度评定,并对结果进行总结,突出该校准项目的重要意义。     

数据采集系统通道间串扰的测试和评价方法

介绍了数据采集系统通道间串扰的成因。根据JJF 1048-1995《数据采集系统校准规范》分别对直流信号对直流通道、交流信号对直流通道以及交流信号对交流通道的串扰能力进行测试、计算和评价,对实验结果进行了分析和总结。研究结果表明了对数据采集系统通道间串扰评价的重要性。     

基于加速度反馈和自抗扰的加筋壁板结构复合振动控制

四面固支加筋壁板结构中存在的模型难以确定等多种不确定因素,影响了闭环结构的振动控制性能.针对这一问题设计了一种不依赖结构数学模型的加速度传感信号反馈和二阶线性自抗扰复合振动主动控制策略,并在理论上分析其稳定性和优越性.首先,采用二阶线性自抗扰控制器实时估计对象模型变化及其外扰组成的广义干扰,并将估计值作为补偿信号前馈到控制信号中消除广义干扰对系统的影响;然后,设计加速度传感信号和线性状态误差反馈的自抗扰复合振动控制器;最后,基于dSPACE实时仿真系统,建立了四面固支加筋壁板结构的主动振动试验平台.利用加速度传感器和压电片驱动器抑制加筋壁板结构振动,并对提出的控制方法进行对比试验.几种外界干扰激励的试验结果表明,该方法不仅能有效抑制由于正弦激励和外界冲击引起的振荡,而且能更好抑制不确定因素引起的整个结构的波动.     

一种新型位移与角度同时测量系统的设计

为了消除悬臂梁移动时产生的阿贝偏角误差,设计了一种可同时测量角度与位移的精密测量系统．首先,在激光干涉原理的基础上,通过改变光路将角度转换为可以反映干涉系统中光程差变化的位移量．其次,采用压电陶瓷（PZT）驱动柔性铰链机构,产生运动的干涉条纹．最后,采用四细分条纹计数辨向方法,进行运动干涉条纹的接收与处理实验,结果表明：在条纹宽度处于合适值时,系统满足了对阿贝偏角精密测量的要求．     

SH wave propagation in piezoelectric coupled plates

The propagation of shear horizontal (SH) wave in a piezoelectric coupled plate is investigated in this paper. Full account is taken of the piezoelectric coupling effect to the isotropic metal core in the mathematical model. One of the applications of this research is in the damage detection of the host metal structure from the wave propagation signal excited by the piezoelectric layer which is surface bonded on the surface of a metal core. This research is distinct from the previous works on SH propagation in piezoelectric structures because the piezoelectric materials were used as the core structure in the previous studies, and the potential of the studies was mainly on time-delay devices. The dispersive characteristics and the mode shapes of the transverse displacement and the electric potential of the piezoelectric layer are theoretically derived. The results from numerical simulations show that the phase velocity of the plate structure tends to the bulk shear wave velocity of the host metal core at high wave number when the shear wave velocity of host plate is larger than that of PZT bonded on it. Furthermore, there are three asymptotic solutions of wave propagation when the shear wave velocity of the host plate is smaller than that of PZT. The mode shape of the electric potential of the piezoelectric layer changes from the quadratic shape at lower wave number and with thinner piezoelectric layer to the shape with more zero nodes at higher wave number and with thicker piezoelectric layer. These findings are significant in the application of wave propagation in piezoelectric coupled structures     

Manufacturing of prestressed piezoelectric unimorphs using a postfired biasing layer

A novel manufacturing method for prestressed piezoelectric unimorphs is introduced and the actuator properties are examined. Prestressed PZT 5A and PZT 5H unimorphs with piezo material thickness of 250 microm and 375 microm were manufactured by using sintering and thermal shrinkage of the prestressing material. The process was carried out by screen printing a layer of AgPd paste on one side of the sintered bulk ceramic. As an alternative method, dielectric low temperature co-fired ceramic (LTCC) tape was used as the prestressing material. Different configurations were tested to obtain high displacements and to make a comparison between materials. After firing, the samples were poled, and the displacement versus load characteristics of the resulting actuators were investigated. A maximum displacement of 118 microm was obtained from a 250 microm thick, prestressed PZT 5H actuator with a diameter of 25 mm, in which LTCC tape was used as the prestressing layer. Similarly, the PZT 5H material provided a maximum displacement of 63 microm with a screen-printed AgPd prestressing layer. The manufacturing method described offers a novel approach for the production of a wide range of integrated active structures on, for instance, an LTCC circuit board. This is especially important because piezoelectric bulk materials with high piezoelectric coefficients can be used to produce high displacements.     

压电微能量采集器PZT厚膜制备及其图形化研究

采用环氧树脂作为中间层的真空键合技术实现体材PZT与硅片键合,再利用机械化学抛光方法将PZT减薄到适当的厚度制备了PZT铁电厚膜,构成了SiO2/Si/SiO2/Epoxy/Ag/PZT/Cr/Cu形式的压电能量采集器悬臂梁结构。基于半导体光刻技术,通过湿法化学刻蚀和切片两种方法实现了PZT厚膜图形化问题,为基于体材PZT厚膜的高性能压电能量采集器的研制打下了良好的基础。     

基于FPGA的高精度压电陶瓷数字驱动电源

 针对压电陶瓷驱动器在六自由度微动平台中的应用,研制了基于FPGA和PA85的六通道高精度数字驱动电源.该驱动电源分为D/A转换和高压线性放大两个模块,D/A转换模块将计算机发出的数字信号指令转换成模拟电压信号输出并进行初级低压放大,高压线性放大模块采用直流放大式电路,将经过初级放大的电压信号进行高压放大.实验结果表明,该驱动电源具有输出精度高、响应速度快、驱动能力强、稳定性好、结构简单、集成度高和调试方便等特点,能有效地应用于六自由度微动平台驱动中.     

Improvement electrical properties of sol–gel derived lead zirconate titanate thick films for ultrasonic transducer application

In this work, a fabrication process of piezoelectric PZT [Pb(Zr_0.52Ti_0.48)O₃] thick films up to 60 μm deposited on silicon and aluminum substrates is reported. Crystalline spherical modified PZT powder about 300 nm in diameter was used as filler. PZT polymeric precursor produced by Chemat Inc. was used as the matrix material. Spinning films were annealed at 700 °C for one hour in the furnace in air. The thickness of the thick films was measured using a scanning electron microscope (SEM). Compared with previous piezoelectric PZT composite films, the modified piezoelectric thick films exhibit better dielectric properties. The dielectric constant is over 780 and dielectric loss is 0.04 at 1 KHz. Using a PiezoCAD model, the high frequency transducer was designed and fabricated. It showed a bandwidth of 75% at 40 MHz.     

Effect of Electric Field on the Response of Clamped-FreeMagnetostrictive/Piezoelectric/Magnetostrictive Laminates

This work deals with the response of clamped-free magnetostrictive/piezoelectric/magnetostrictive laminates under electric field both numerically and experimentally. The laminate is fabricated using two magnetostrictive Terfenol-D layers and a soft piezoelectric PZT layer. Easy axis of Terfenol-D layers is length direction, while the polarization of PZT layer is the thickness direction. The magnetostriction of the Terfenol-D layers bonded to the upper and lower surfaces of the PZT layer is first measured. Next, a nonlinear finite element analysis is employed to evaluate the second-order magnetoelastic constants in the Terfenol-D layers bonded to the PZT layer using measured data. The induced magnetic field and internal stresses for the laminates under electric field parallel to the poling are then calculated and discussed in detail. In addition, the induced magnetic field is measured, and test results are presented to validate the predictions.     

Microwave Hydrothermal Synthesis PZT of Nanometer Crystal

It was focused on the applications and developments of microwave hydrothermal synthesis piezoelectric ceramic powder. The microwave hydrothermal vessel was designed and manufactured. The microwave hydrothermal synthesis system was established and the PZT piezoelectric ceramic powder was synthesized. XRD and TEM have been used to characterize the products in detail. The diameter of the PZT powder particle is from 40 to 60 nm.     

光杠杆纳米微位移测量系统中的信号处理

本文提出了一种基于光杠杆原理非接触式的纳米级微位移测量系统.该系统通过光学方法对微位移量进行放大,光学放大倍数高,该系统的理论分辨率可达4nm,实际测得静态分辨率小于10nm.信号处理采用基于高精度一维PSD的信号探测电路,并且通过设计有效地抑制了噪声和干扰.实验中使用PZT作为被测物的微小位移驱动器,与电容测微仪JDC-Ⅱ所测数据进行了验证比较,系统所测得的数据证明了其正确性和可行性.并且该系统受温度影响小,结构简单,便于使用MEMS技术集成和微型化.     

Flexible ultrasonic transducers

Flexible ultrasonic transducers (UTs) consisting of a metal foil, a piezoelectric ceramic film, and a top electrode have been developed. The flexibility is realized owing to the porosity of piezoelectric film and the thinness of metal foil. In this paper, the stainless steel (SS), lead-zirconate-titanate (PZT)/PZT composite and silver paste were chosen as metal foil, piezoelectric film, and top electrode materials, respectively. The SS foil serves as both substrate and bottom electrode. The PZT/PZT piezoelectric composite film is made by the sol-gel spray technique. PZT/PZT films of thicknesses from 40 to 70 microm were fabricated onto SS foils. The capability of these flexible sensors operated in the pulse-echo mode for nondestructive testing on flat and curved surfaces of different materials at room temperature and 160 degrees C has been demonstrated. Numerical simulations of the effects of the metal foil thickness on the ultrasonic performance of flexible UTs also were carried out, and the results are in reasonable agreement with experimental data. In addition, a PZT/PZT flexible transducer showed a signal strength comparable with that obtained by a commercial room temperature broad bandwidth transducer.