基于氧化石墨烯的ST-cut声表面波高性能湿度传感器

开发了氧化石墨烯(GO)涂覆的ST-cut石英声表面波(SAW)湿度传感器。SEM和FTIR研究发现GO表面呈现起伏褶皱状且含有亲水性基团,这有利于薄膜对水分子的吸附;还发现SAW湿度传感器的频移响应由质量负载效应提供,且高湿度下传感器频移的指数增加归因于水凝结引起的阻尼效应。该传感器具有良好的灵敏度、几乎为零的温度系数、稳定的短期重复性与长期稳定性,且成本低,为湿度传感的研究提供了较好的选择。     

面向恶劣环境的基于AlN/4H-SiC材料的声表面波谐振器设计与制作（英文）

目的:在高温等恶劣工作环境下,燃气轮机有着迫切的温度等工况参数的实时监测需求。声表面波(SAW)技术与微机电系统(MEMS)技术的结合可提供一种很有发展前景的解决方案。本文旨在探讨SAW谐振器的设计与仿真方法,研究高质量c轴择优取向的AlN压电薄膜制备工艺及与MEMS工艺兼容的SAW谐振器制作工艺,并测试其电学性能以验证SAW谐振器设计与制作的正确性与可行性。创新点:1.首次在耐高温材料AlN/4H-SiC上设计、仿真及制作SAW谐振器并测试电学性能;2.在4HSiC上得到了高质量c轴择优取向的Al N压电薄膜并开发了一套与MEMS工艺兼容的SAW谐振器制作工艺。方法:1.通过对SAW谐振器所有结构参数的设计与仿真,得到谐振器的谐振频率与反谐振频率等(图2和3);2.利用磁控溅射方法在4H-SiC衬底上溅射高质量c轴择优取向的AlN压电薄膜,再利用光刻、湿法腐蚀等MEMS工艺制作SAW谐振器(图4);3.通过扫描电镜和X射线衍射等手段,检测AlN压电薄膜质量(图5和6)及器件制作结果(图7);4.利用网络分析仪测试SAW谐振器电学性能并与仿真结果相比较,验证SAW谐振器设计仿真方法和MEMS制作工艺的可行性和有效性(图8)。结论:1.基于耐高温材料AlN/4H-SiC,成功设计并制作出SAW谐振器(尺寸:1107μm×721μm);2.在4H-SiC上得到了高质量c轴择优取向的AlN压电薄膜,衍射峰为36.10°,摇摆曲线半高宽仅1.19°;3.SAW谐振器电学性能测试结果与仿真结果一致,证明其设计仿真方法正确有效、MEMS制作工艺可行。     

SAW动态转矩传感器理论计算与推导

动态转矩的测量对于机械传动过程的监测和控制具有重要意义,现有的测量方式大都是有源接触式的测量,多具有接触滑片磨损和测量精度下降等问题。本实验采用声表面波(SAW)技术的动态转矩测量方法。通过分析其工作原理,以典型ST切片石英基体材料为例,推导SAW器件谐振频率与转矩的关系表达式,提出采用差分连接方式来消除温度对于测量结果的影响,并简要分析测量系统的构成与工作原理。     

基于FPGA的数字频率计VHDL软件实现方法

运用VHDL在FPGA/CPLD器件上实现一种数字频率计测频系统,分析了数字频率计软件构成结构,并对其中的测频控制信号发生器电路进行了VHDL软件编程实现。     

基于FPGA的数字频率计VHDL软件实现方法

运用VHDL在FPGA/CPLD器件上实现一种数字频率计测频系统,分析了数字频率计软件构成结构,并对其中的测频控制信号发生器电路进行了VHDL软件编程实现。     

SAW reflection and scattering by electrodes

INTRODUCTION Electrodes or grooves in the path of surface acoustic wave (SAW) propagation give rise to SAW reflection and cause SAW scattering into bulk acous- tic wave. This is a fundamental SAW problem on which had been conducted many studies. It is espe- cially important for designing SAW radio frequency identification tags (RFID). Global SAW Tag (GST) (Hartmann, 2004) has many advantages over tradi- tional SAW RFID, but requires accurate knowledge of the reflectivity and …     

关于石英晶体频率稳定度高的论述

石英晶体振荡器的频率稳定度很高,主要是因为晶体振荡器具有很强稳频能力,晶体振荡器作为振荡元件时,等效为一个电感元件Le,当由于某种原因使得频率f增加时,Le也增加很多,根据频率f=1/2π√LeC,当Le增加时f就会下降,达到了自动稳频的目的,正是由于以上这些原因,使得石英晶体振荡器的频率稳定度很高。     

介质谐振器材料、电性测量和分米波滤波器

1引言介质谐振器是指能替代传统的、各种以空气为介质的金属谐振腔的小型无源谐振器件。制作该类器件（包括滤波器）的材料常称介质谐振器材料。该类材料除满足一般微波介质材料的要求外，对它的特殊要求主要有：高介电常数（高ξ~'_r）、低介质损耗（低tanδ或高Q因子）和谐振频率的温度系数接近于零（τ_f≈0）。自1939年B．Q．Richtmeyer提出介质陶瓷材料可作为谐振器的设想以来，1963年发现了化镓的耿氏效应，1965年出现化镓微波固态源，紧接着发展了微带线和化镓场效应管，微波电路的小型化和集成化的焦点就集中在稳频腔和滤波器的小…     

SPWM稳频稳压逆变电源测量系统分析与研制

介绍了SPWM稳频稳压逆变电源的设计方案，重点分析了其测量系统，该电源设备通过取样检测电机实际响应电压Vpwm，解决了SPWM脉宽调制式变频器与电机的匹配问题。     

RC桥式正弦波振荡器的实践分析

RC桥式正弦波振荡器在文献中也称之为RC文氏电桥式振荡器,由选频、反馈、放大和稳幅四个部分组成。在实用电路中往往将选频网络和正反馈网络合二为一,并采用两级放大,目的不仅是满足了振荡所需要的相位条件,而且还具有放大和稳幅的作用。RC桥式正弦波振荡器是一个输出外供信号的信号源,上电后就能输出一定频率的正弦波电压信号,但振荡信号频率较低,一般在1MHz以下。     

Use of superposition principle to derive a general mathematical model to simulate one-to-one, one-to-multi and multi-to-multi saw filter designs

This paper explains and summarizes a new attempt to derive a general mathematical model [GMM] to simulate surface acoustic wave (SAW) filters, using the superposition principle and delta function model. GMM can be used to simulate One-to-One, One-to-Multi and Multi-to-Multi SAW filter devices. The simulation program was written using MATLAB (the language of technical computing). Four-design structures (One-to-One, One-to-Two, One-to-Three and Ten-to-Ten) ware selected to test the correctness of GMM. The frequency response of the simulation and test results are similar in center frequency and 3-dB bandwidth, but the insertion loss is different, because of some second order effects (Issa Haitham, 1999).     

USE OF SUPERPOSITION PRINCIPLE TO DERIVE A GENERAL MATHEMATICAL MODEL TO SIMULATE ONE-TO-ONE,ONE-TO-MULTI AND MULTI-TO-MULTI SAW FILTER DESIGNS

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Research on transmission performance of a surface acoustic wave sensing system used in manufacturing environment monitoring

Surface acoustic wave (SAW) sensors show great promise in monitoring fast-rotating or moving machinery in manufacturing environments, and have several advantages in the measurement of temperature, torque, pressure, and strain because of their passive and wireless capability. However, very few studies have systematically attempted to evaluate the characteristics of SAW sensors in a metal environment and rotating structures, both of which are common in machine tools. Simulation of the influence of the metal using CST software and a series of experiments with an SAW temperature sensor in real environments were designed to investigate the factors that affect transmission performance, including antenna angles, orientations, rotation speeds, and a metallic plate, along with the interrogator antenna–SAW sensor antenna separation distance. Our experimental measurements show that the sensor’s optimal placement in manufacturing environments should take into account all these factors in order to maintain system measurement and data transmission capability. As the first attempt to systematically investigate the transmission characteristics of the SAW sensor used in manufacturing environment, this study aims to guide users of SAW sensor applications and encourage more research in the field of wireless passive SAW sensors in monitoring applications.     

机床夹具定位误差的计算机辅助计算

机床夹具定位误差计算是夹具设计中必不可少的工作，该项工作比较繁琐并很容易出错。若利用计算机进行辅助计算，不仅计算准确，而且还可以减轻设计人员的劳动。本利用夹具定位原理推导建立了通用数学模型，并统制了计算机辅助计算程序，也适用于其它定位元件定位误差的计算。     

Research progress in SAW filter banks

INTRODUCTION SAW (Surface Acoustic Wave) filter bank is a single input, single or multi-output device consisting of multi-SAW-filters, input interconnection network or switch circuits, and can be divided into two cate- gories: channelizer (multi-output) and switchable (programmable, single output). The former is mainly used in military channelized receiver for spectrum analysis; the latter has wide application in frequency synthesizer and frequency-hopping radar and com- munication syst…     

PRO-ESPRIT 算法在声表面波标签识别中的应用

The surface acoustic wave (SAW) identification (ID)-tags have great potential for application in radio frequency identification (RFID) due to their characteristics of wireless sensing and passive operation. In the measurements based on the frequency domain sampling (FDS), to expand the range of detection and allow the system work in harsh environments, it is necessary to enhance the identification capability at low SNR. In addition, to identify the tags in real time, it is important to reduce identification time. Therefore, estimation of signal parameters based on the Procrustes rotations via the rotational invariance technique (PRO-ESPRIT) is adopted. Experimental results show that good identification capability is achieved with a relatively faster measurement speed.     

Numerical Simulation of Surface Acoustic Wave and Detection of Surface Crack in Steel

The surface acoustic wave (SAW) propagating in a sample of steel is simulated by using finite element method (FEM). The waves are excited by a load function with propagation properties such as phase velocity dispersion and wide bandwidth. A two-dimensional model consisting of surface defects loaded with a wideband 50-200 MHz and short time 0.1 μs displacement function is investigated in the time and frequency domains. By transient dynamic analysis, Fourier transform and dispersion calculation, snapshots of propagating wave and responses from sensing points are presented. It is indicated that this supervision approach is sensitive to the surface cracks and reflections.     

Dynamic Monte Carlo study on the probability distribution functions of tail-like polymer chain

INTRODUCTION Polymer chains with one end attached to a sur- face by means of physical or chemical interaction have become one of the important polymer science subject, which are useful for many applications, such as polymer compatibilizers, copolymer microphases, colloid stabilization, polymeric surfactants (Milner, 1991). Grafting polymers can improve the power efficiency of electrorheological fluids, enhance pho- toluminescence of nano materials, and increase dis- persion stability. On …     

超声治疗仪的设计与研制

超声治疗仪包括工作台、支架和治疗面板。研制的超声治疗仪体积小、可定时、操作简单、实用性强,可根据治疗需要调节功率和频率。经试用,该仪器性能稳定,数据准确,治疗效果好。