硅微谐振式压力传感器中的单端口静电激励-电容检测方法研究

采用静电激励-电容检测方式的硅微谐振式压力传感器具有温度稳定性好、灵敏度高、功耗低等优点,但同频耦合干扰是限制电容检测精度的主要因素。采用频域分离法可有效地克服同频耦合干扰带来的影响。在研究基于频域分离法的单端口静电激励/电容检测的基础上,提出了单端口静电激励/电容检测方案。     

一种电容层析成像系统电极组合激励测量方法

针对电容层析成像图像重建具有非线性不适定性的问题,提出了8组24电极旋转激励测量方案,并与传统12电极电容层析成像传感器进行了对比分析,包括电容值大小及其动态范围、敏感场分布均匀性以及重建图像质量。应用COMSOL软件及Matlab软件对两种传感器激励模式进行仿真,结果表明:所提出的8组电极旋转激励测量模式,其电容独立测量数与传统12电极传感器相近,可较好地保证实时成像速度,测量电容值较大且动态范围较小,降低了信号检测电路设计难度,测量区域灵敏场均匀性有所改善,对中心物体的成像质量明显提高。     

基于ECT的聚合物锂电池组内部电容率检测装置设计

针对聚合物锂电池组温度分布均匀性难以全面、准确评估的问题,应用电容层析成像检测电池组内部电容率以间接实现电池组温度分布均匀性评估,并开发聚合物锂电池组内部电容率检测装置。该装置利用高频交流信号激励ECT传感器,C/V转换电路将电容转换为成正比的电压,经过信号调理后,上位机获得电池组内部电容率分布。实验结果表明测量装置重复测量误差在0.068 63 n F/m以内,电容率的分布呈现对称性,与电池组的内部构造相吻合,装置具有良好的重复性和可靠性。     

三维电容层析成像组合电极激励测量模式

针对3层电容阵列电极传感器,基于三维仿真,研究了两种组合电极激励测量模式,并与传统的单电极激励单电极测量模式进行了比较,包括电容测量值大小及其动态范围、敏感场分布均匀性以及重建图像质量。基于COMSOL软件及Matlab软件进行了仿真实验,结果表明:相较于传统的单电极激励单电极测量模式,组合电极激励测量模式所得图像重建效果更好,测量电容值较大且动态范围较小,敏感场分布更加均匀,对中心物体的成像质量明显提高。     

半球谐振子固有刚性轴方位角测量方法与仿真研究EI北大核心CSCD

半球谐振子固有刚性轴方位角测量是谐振子制造及调平等工艺过程的重要基础。首先对半球谐振子固有刚性轴方位角的测定方法进行了理论分析,其次开展了基于位置激励的半球谐振子谐响应仿真研究,模拟了固有刚性轴位置的测定过程,最后通过设计试验,采用非接触式声波激励,激光多普勒测振仪采集唇缘不同位置的振动信号,完成了半球谐振子固有刚性轴方位角的测定。该方法的角度分辨率优于1°,结果表明:其固有频率主轴方位角的辨识误差约为4.4%,具有良好的可行性,该方法装置简单、便于操作,对半球谐振子初期研制过程中固有刚性轴方位角的精确定位具有重要的参考意义。     

静电力平衡式MEMS电容薄膜真空计检测电路研究

静电力平衡式MEMS电容薄膜真空计量程宽、稳定性高,具有广阔的应用前景。测量电路是保证静电力平衡式MEMS电容薄膜真空计性能的关键因素。采用交流激励式检测方法,设计了一种微小电容检测电路,并利用软件仿真和实验测试进行验证。结果表明,该电路能够快速检测微小电容并将其转换为直流电压信号,分辨率为0.33 V/pF。此外,抗驱动电压干扰测试表明,该电路能够在1～100 V范围的直流驱动电压下正常工作,电容测量的输出电压最大标准差为0.010 249 V,并且具有优异的稳定性。     

带状注速调管单端口输入腔的场形平衡方法

对X波段带状注速调管单端口输入腔中间隙纵向电场(电子注方向)的场形平衡问题进行了研究.通过在另一侧腔体外加载封闭波导,使其内部的电场场形可以在一定范围内进行调整.这种方法简化了驱动装置,并能避免双端口激励方法中输入信号相位不一致引起场形失衡的问题.使用CST软件进行模拟计算获得了较好的优化结果,随后为验证该方法的有效性,使用加工的冷测模型对单端口耦合的输入腔进行了测试,实验结果表明:加载平衡波导可以有效的改善场分布,此外,通过改变调谐钉深度和加载波导侧的耦合孔尺寸对场分布也有明显的调节作用.     

桥式推挽结构超声激励电路性能分析

基于桥式推挽结构,设计了由两路正向单脉冲电压产生双极性电压效果的电路,提高了激励信号的能量,为超声无损检测激励电路的负向耐压低、供电电源复杂等问题提供了解决方案。该方案包括硬件实现和相关实验验证。脉冲回波检测实验结果证明:桥式推挽结构的超声激励可以提高回波的幅度,在相同实验条件下,回波幅度为单极性方波脉冲激励的两倍,等效于双极性方波脉冲激励的效果。该文方法可以提高超声激励电路的性能,为高性能便捷式超声激励系统的设计提供了理论和实验依据。     

基于单端口多模态微悬臂梁的谐振式大量程智能气体传感器(英文)

基于悬臂梁的谐振气体传感器可以通过测量悬臂梁谐振频率的偏移而检测相应气体分子.本文介绍了一种使用自激励自检测(SAD)电路驱动单端口多模态微悬臂梁的智能谐振式气体传感器.这种激励模式简化了悬臂梁结构和微加工过程.另外,还可以通过便捷地改变悬臂梁谐振模态实现大量程的气体浓度检测.通过仿真分析了不同模态下悬臂梁的模型和敏感度.通过测量这种基于单端口多模态悬臂梁的气体传感器对于气体的响应情况,展示了这种多模态SAD系统以及其改变模态增加测量量程的功能.     

电容式射频微机械谐振器芯片级测试技术

针对用电容式射频微机械谐振器芯片级测试时信号微小、寄生效应严重、从而使得激励和检测困难的问题,本文对基于固支梁的微机械谐振器的电学测试理论和技术进行了研究.利用机电类比的方法得到了包含寄生参数的谐振器的等效电路并利用安捷伦的ADS电路仿真软件进行模拟.根据电路仿真结果分析了谐振器寄生参数对测试结果的影响,并在此基础上搭建了经过良好电磁屏蔽设计的谐振器单端口电学测试平台.使用合适的偏置,对谐振器进行了芯片级测试.得到了一个8.6 MHz谐振器的幅度——频率响应特性曲线,其结果与设计值相符.     

半球谐振子超精密修调方法研究

目的 研究因谐振子质量缺陷而引起的频率裂解机制,进而对刚性轴位置进行质量高分辨率可控去除,提高陀螺精度。方法 首先基于多区域配合划分法建立半球谐振子高精度有限元仿真模型,分析质量大小与位置对谐振子频差的影响规律。其次搭建谐振子振动特性检测平台,利用拍频法实现其频差值和刚性轴位置的精确辨识。最后结合仿真与辨识结果以及离子束加工方法确定谐振子超精密修调方案。结果 优化网格划分方法后,谐振子有限元模型频差值小于0.000 1 Hz,当修调定位误差相同时,在一个范围内的质量去除比单点质量去除的修调效率更高;谐振子质量缺陷四次谐波刚性轴位置辨识精度可达0.1°,与常见的幅值法相比,其精度提高了一个数量级;通过三次点线结合方式进行质量修调后,谐振子频差值小于0.001 Hz,修调效率与精度得到了提升。结论 提出的谐振子仿真模型、振动特性测试方法以及离子束修调工艺精度较高且可行性较强,对实现半球谐振子性能高精度检测以及高质量加工具有重要意义。     

参数激励下碳纳米谐振器的非线性振动研究

该文研究了两端固支情况下的碳纳米管谐振器在直交流电激励作用下的非线性振动响应。考虑外激励频率接近其固有频率的主共振情况下以及几何非线性,忽略静电力的非线性、范德瓦耳斯力和初始静变形的影响,运用欧拉伯努利连续梁理论,通过哈密尔顿原理得到非线性控制方程。然后利用伽略金方法离散得到降阶方程,最后应用摄动分析方法获得其振动响应的幅频曲线。主要分析了阻尼、直交流电荷载、几何三次非线性项对响应的影响。结果表明几何三次非线性项直接影响碳纳米管谐振器在外激励作用的振动响应以及碳纳米管在交流电荷载作用下的振动响应相对于直流电荷载更加敏感,并在一定程度上发生软化行为等。     

用于气体检测的热激励MEMS悬臂梁谐振器

笔者设计了一种电热激励压阻检测的微悬臂梁谐振器．悬臂梁上的敏感层吸附特定的气体后,可以通过测量质量变化所导致的悬臂梁谐振频率的变化而得出待测气体的浓度．该谐振器的加工基于SOI硅片和ICP刻蚀技术．通过有限元仿真得出了悬臂梁的应力温度分布曲线,从而证实了该方案可以提供比普通结构更适宜于气体敏感材料工作的温度分布．从理论和实验上分析了谐振器在不同激励电压下的频率响应．实验结果表明,该谐振器具有较高的谐振频率和品质因数,其激励电压与振动幅值成线性关系．     

Doubly rotated contoured quartz resonators

Doubly rotated contoured quartz resonators are used in the design of temperature-compensated stable clocks and dual-mode sensors for simultaneous measurements of pressure and temperature. The design of these devices is facilitated by models that can predict frequency spectra associated with the three thickness modes and temperature and stress-induced frequency changes as a function of crystalline orientation. The Stevens-Tiersten technique for the analysis of the C-mode of a doubly rotated contoured quartz resonator is extended to include the other two thickness modes. Computational results for harmonic and anharmonic overtones of all three thickness modes of such resonators help in optimizing the radius of curvature of the contour and electrode shape for suppression of unwanted modes and prevention of activity dips. The temperature and stress-induced changes in thickness-mode resonator frequencies are calculated from a perturbation technique for small dynamic fields superposed on a static bias. The static bias refers to either a temperature or stress-induced static deformation of the resonator plate. Phenomenological models are also used for calculating the temperature and stress-induced changes in resonant frequencies as a function of crystalline orientation. Results for the SBTC-cut quartz plate with a spherical convex contour of 260 mm indicate that normal trapping occurs for the third (n=3) and fifth (n=5) harmonic of the A-mode, the fundamental (n=1) and third (n=3) harmonic of the B-mode, and the fundamental (n=1) and fifth (n=5) harmonic of the C-mode     

A perturbation method for predicting the temperature and stress sensitivities of quartz vibrating structures simulated by finite-element analysis

Thermal and mechanical sensitivities of vibrating structures and wave guides are key parameters for the optimization of high stability resonant devices operating in the ultrasonic frequency range (from a few tenth of kilohertz to a few gigahertz). In this paper, the possibility to simulate and predict temperature coefficients of frequency (TCF) of quartz transducers of any shape as well as their stress sensitivity coefficients is addressed. The theoretical developments based on harmonic finite-element analysis coupled with a variational perturbation method are detailed, showing how to derive the regarded parameters. The proposed approach is validated using a two-dimensional (2-D) model of a plane face-bulk acoustic resonator for which an analytical model can give access to both TCF and stress sensitivity coefficients. It is then applied to a 2-D model of convex plane bulk acoustic resonator of singly rotated quartz and used to compute the first order TCF of a 3-D model of a tuning fork structure. In the latter case, the importance of considering the actual excitation of the device is demonstrated, allowing for the accurate definition of angular loci for which thermal compensation can be expected, in agreement with literature. Possible extensions and improvements of the proposed method is discussed in conclusion.     

Design of chirp excitation waveform for dual-frequency harmonic contrast detection

Tissue background suppression is essential for harmonic detection of ultrasonic contrast microbubbles. To reduce the tissue harmonic amplitude for improvement of contrast-to-tissue ratio (CTR), the method of third harmonic (3f₀) transmit phasing uses an additional 3f₀ transmit signal to provide mutual cancellation between the frequency-sum component and the frequency-difference component of tissue harmonic signal. Chirp excitation can further improve the SNR in harmonic imaging without requiring an excessive transmit pressure and thus reduce potential bubble destruction. However, for effective suppression of tissue harmonic background in 3f₀ transmit phasing, the 3f₀ chirp waveform has to be carefully designed for the generation of spectrally matched cancellation pairs over the entire second harmonic band. In this study, we proposed a chirp waveform suitable for the method of 3f₀ transmit phasing, the different-bandwidth chirp signal (DBCS). With the DBCS waveform, the frequency-difference component of tissue harmonic signal becomes a chirp signal similar to its frequency-sum counterpart. Thus, the combination of the DBCS waveform with the 3f₀ transmit phasing can markedly suppress the tissue harmonic amplitude for CTR improvement together with effective SNR increase of contrast harmonic signal. Our results indicate that, as compared with the conventional Gaussian pulse, the DBCS waveform can provide 6-dB improvement of SNR in 3f₀ transmit phasing with a CTR increase of 3 dB. Nevertheless, the limitation of available transmit bandwidth and the frequency-dependent attenuation can degrade the performance of the DBCS waveform in tissue suppression. The design of the DBCS waveform is also applicable to other dual-frequency imaging techniques that rely on the harmonic generation at the difference frequency.     

High-power free-electron maser with frequency multiplication operating in a shortwave part of the millimeter wave range

The possibility of using frequency multiplication in order to obtain high-power short-wavelength radiation from a free-electron maser (FEM) with a Bragg resonator has been studied. Preliminary experiments with an LIU-3000 (JINR) linear induction accelerator demonstrate the operation of a frequency-multiplying FEM at megawatt power in the 6- and 4-mm wave bands on the second and third harmonic, respectively.     

Generation of High-Frequency Harmonics in the Case of Large-Amplitude Vibrations of a Gas in a Closed Tube

Based on the model of a viscous compressible heat-conducting gas, the author investigates numerically the vibrations of a gas column in a closed tube in excitation by a flat piston that moves according to a harmonic law with an amplitude comparable to the resonator length. Consideration is given to the process of transformation of the mode and frequency of vibrations of the gas column for a fixed excitation frequency; the transformation is accompanied by a change of the type of resonance and is related to the increase in the eigenfrequency of the system due to the increase in the average temperature of the gas.     

Overtone Oscillator for SAW Gas Detectors

A design of an overtone oscillator a with surface-acoustic-wave (SAW) resonator is described in this paper. The circuit works stably on the frequency 4.710 GHz (29th harmonic of loaded resonator) at about the -2 dBm level. In the construction, distributed-constant circuits have been applied. Commercially available SAW sensors usually work within the range of frequency from a few dozen to a few hundred megahertz. On the other hand, it is a well-known fact that the mass sensitivity of such devices is directly proportional to the square of its operating frequency, and SAW sensors for organic vapors, for instance, are usually mass sensitive. For this reason, an increase in the SAW sensors' operating frequency seems to be useful. The circuit described in this paper shows the possibility of a dramatic rise in SAW operating frequency by exerting its operation through a specific high overtone (harmonic frequency) of the SAW resonator. The overtone frequency in such a solution then plays the role of basic mode. The oscillator proposed in this paper seems to be a good tool for chemisensitive-SAW-coating investigation     

Photoacoustic Excitation of the Interior Surface of an Acoustic Resonator for Speed of Sound Measurement

A remote optical technique is proposed as a valid alternative to conventional electroacoustic excitation of sound inside an acoustic resonator. Efficient photoacoustic conversion of an amplitude-modulated light beam, impinging on the interior solid surface of the resonator wall, into a stationary acoustic field is achieved. The reported results were obtained in a cylindrical stainless steel resonator with a volume of about 572 cm³; the radiation source is the 514 nm line of an Ar⁺ laser. The laser beam can be focused on different points of the resonator internal surface. The signal frequency dependence is well interpreted in terms of gas-microphone detection theory. The precision obtained in the measurement of resonance frequency f _N and halfwidth g _N of the cavity modes is on the order of 10^-6 of f _N and is likely to be further improved by minor refinements of the experimental apparatus.