PVDF压电传感器在实验模态分析中的应用

提出通过聚偏氟乙烯(PVDF)压电传感器替代加速度计对振动结构进行实验模态分析。在固支梁表面分别布置矩形PVDF压电传感器和加速度计,测量外界激励与振动结构响应之间的频率响应函数,通过模态软件对数据进行分析,得到模态参数并将结果进行对比。实验结果表明,利用PVDF压电传感器对振动结构进行实验模态分析效果良好,且具有附加质量小,频响宽,操作简便等特点,与加速度计相比,具有明显的优越性。     

MEMS微加速度计在振动环境下的可靠性研究

由于微加速度计的可靠性成为其产品商业化过程中的一个重要问题,而冲击断裂是导致其性能失效的主要原因。主要研究了压阻式微加速度计在振动环境下的可靠性问题。设计了微加速度计在振动环境下的可靠性试验并通过ANSYS进行仿真。经过分析得出微加速度计在振动环境下的主要失效模式,并进行了相应的失效机理分析。通过可靠性实验进行了验证,对微加速度计在振动环境下的可靠性进行评估,并描绘了其可靠度与失效概率曲线。     

基于SOI硅片高g值加速度计的设计与分析

基于SOI硅片,设计了一种新型平面内振动高g值压阻式加速度计。该加速度计包括X轴向与Y轴向单元,采用三梁一扇形质量决平板内振动结构,与传统的平面外振动结构相比较,该结构具有较高的谐振频率与灵敏度。采用两两相对的单元布局方式,可有效的消除横向灵敏度的影响,提高结构的测量精度。建立理论模型并利用ANSYS软件对结构进行模拟分析与验证。分析表明,加速度计在X轴向、Y轴向灵敏度分别为1.2μv／g、1.18μv／g;谐振频率分别为479KHz、475KHz。可实现对量程高达25万g加速度的测量。     

MEMS加速度计在振动环境下的可靠性分析

以电容式MEMS加速度计的悬臂梁结构为研究对象,分析了振动环境下MEMS加速度计的典型失效模式及失效机理;在Miner理论的基础上,引入了应力-寿命曲线,建立了疲劳可靠性模型;在考虑强度退化前提下,基于应力强度干涉理论建立了塑性形变可靠性模型;运用蒙特卡洛法验证了两种可靠性模型的准确性,并分析了模型关键参数对可靠度的影响。结果显示,振动应力水平和材料的屈服强度对可靠度有显著的影响,减小应力幅值,增大屈服强度,可以提高MEMS加速度计的可靠性。     

MEMS低量程微加速度计的设计

在传统双边四梁微加速度计结构的基础上,设计了一种新型MEMS低量程微加速度计,量程为±10 g。用ANSYS有限元软件对加速度计的结构建立仿真模型,进行应力、模态及抗冲击能力分析。加速度计供电电压为5 V时,灵敏度理论值达到1.029 mV/g,与传统结构相比,极大地提高了低量程微加速度计的灵敏度。     

高灵敏度QVBA限位结构设计研究

石英振梁加速度计(QVBA)具有检测精度高、准数字输出的特点,灵敏度是影响其性能的一个重要指标参数。针对现有石英振梁加速度计灵敏度低的问题,设计了一种高灵敏度石英振梁加速度计。它采用在石英摆片上下位置施加一对限位片,既可对石英摆片的最大位移量进行限制以提高器件的抗冲击性能,又可增加石英摆片振动过程中的阻尼力以提高器件的抗振动性能,降低了加速度计一阶模态谐振频率的限制条件,有效提高了加速度计的灵敏度。最后依据加速度计的结构特点设计出了相应的工艺制作方案,并加工出了差分结构的加速度计样机,经测试其灵敏度为65.74Hz/g,10min零位稳定性为15.8μg。     

单轴摆式伺服线加速度计悬丝断裂故障的分析

简单介绍了单轴摆式伺服线加速度计的结构和工作原理,并结合加速度计生产测试、装机使用等环节,对加速度计上电快慢及加速度计幅相频动态特性的关系进行了研究分析,找出了生产测试中导致加速度计悬丝断裂故障的重要原因。     

基于高速摄像技术的管系振动位移测量

针对试验中高速摄像技术在远距离测量振动响应精度较低的问题,提出结合双三次 插值法与Sobel算子边缘检测图像技术的方法,用其处理测得图像来提高测量精度。首先,设计了采 用高速摄像与加速度计两种测量系统的管系振动台试验。然后,对高速摄像系统测得的图像 与加速度计测得的加速度振动响应进行处理并提取位移振动响应数据。最后,从时域和频域 两个角度对比高速摄像与加速度计两种测量系统测得的位移振动响应数据,对高速摄像系统 测得数据的准确性进行分析。结果表明,结合双三次插值法与Sobel算子边缘检测图像处理 技术优化高速摄像技术测得的图像可以获得满足测量与使用要求的高精度位移振动响应数 据。     

三轴加速度计在水下结构振动测试中的应用

采用基于MEMS技术的ADXL330三轴加速度计芯片,设计了适合水下结构振动测试的加速度传感器,并应用于某输水管线闸门振动监测系统中。分析了ADXL330结构、原理和标定方法。根据水下结构振动测试特点和要求,设计了应用电路、防水结构以及振动测试系统。现场应用表明,采用该芯片设计的三轴加速度传感器能够满足水下结构振动监测的需要,具有低成本、高精度、易安装和安全可靠等特点。     

一种小型电容敏感式加速度计的研制

利用弹性良好的铍青铜为材料制作加速度计中的敏感振动元件,研制出电容敏感式加速度计。设计了一种提取差动电容信号的检测电路。给出了电路中所使用的电子元器件,经分析求解得出了电路的输出电压和传感器信号拾取电容变化量之间的正比例关系。经过实验测试,加速度计的灵敏度大约为391.12mV/(m.s-2)。     

传输矩阵法分析多环高阶谐振滤波器特性

与输入／输出波导耦合的环型谐振腔能形成结构简洁、性能良好、集成度高的信道滤波器。为实现通带内频率响应平坦度高、滚降时间快的滤波效果,采用多环结构形成的高阶滤波器。利用传输矩阵法推导了环与环问通过串联耦合和并联耦合两种方式形成的多环高阶谐振滤波器的传输甬数公式。对于并联耦合结构,通过优化直接影响下话路滤波特性的环与环间直波导的长度,实现了下话路光谱的对称性。对于串联结构,影响其特性的主要因素为环与环间的耦合系数．要实现最大平坦的通带特性,通过数值计算得出各个环间耦合系数必须从中间到两侧对称增加的特性。     

A Novel Dual-Wavelength DFB Fiber Laser Based on Symmetrical FBG Structure

A novel grating structure is proposed and demonstrated to obtain stable dual-wavelength (DW) distributed-feedback (DFB) fiber lasers at room temperature. The proposed grating is based on a symmetrical structure, where one half is periodically sampled by "0"-to-"pi" period and the other half is done by "pi"-to-"0" period. This structure can create two separated resonance cavities and hence achieve the stable DW lasing operation. By fabricating the proposed grating on a piece of Er : Yb-codoped fiber, we experimentally obtain a stable DW-DFB fiber laser with wavelength spacing of ~440 pm at room temperature     

硅功率场效应晶体管的研究

由于采用了“二氧化硅隔离准平面结构”制作硅结型垂直沟道功率场效应晶体管,使器件频率特性有了明显提高,分别在800MHz和1000MHz下得到了10W与8W的输出功率,其功率增益大于7分贝.这种器件可应用在P～L频段.本文从器件的等效电路出发,提出了这种高频功率器件在作结构设计时应遵循的基本原则;简略地介绍了“二氧化硅隔离准平面结构”的特点;着重指出了研制中应注意的问题;最后,简述了影响器件直流参数的有关因素.     

An Improved Lattice Filter Structure with Minimum Roundoff Noise Gain

In this paper, a new filter structure is derived by combining the lattice structure and error feedback technique, which contains a free parameter used for structure optimization. The roundoff noise of the proposed structure is analyzed, and the corresponding mathematical expression is deduced. The problem of how to optimize the free parameter is investigated in terms of minimizing the roundoff noise gain. When the free parameter is expressed as an integer power-of-two, for an Nth-order digital filter, the proposed structure requires \(5N+1\) multipliers, which yields the same implementation complexity as the normalized lattice structure. A numerical example is given to show the finite wordlength performance of the proposed structure.     

磁光盘数据信道不对称性对其噪声抑制能力的影响

针对磁光数据存储系统．研究了差分读出信道的结构不对称性对其噪声性能的影响。研究中发现,差分信道抑制共模噪声的能力取决于信道参数的匹配程度。另外还发现．信道结构不对称将导致信道在读取数据“１”和数据“０”时．信道的噪声强度不同。     

Theoretical Aspects of Microstrip Waveguides

The Microstrip is a modification of the wire-above-ground system of transmission - the wire is replaced by a narrow strip printed on a dielectric sheet which is backed by a conductor. An exact theory for such a structure is difficult because the cross section is not homogeneous and has a geometry which does not lead to separation of variables. Furthermore it is an "open" structure where the energy is not confined to a finite region as it would be in conventional or "closed" waveguides.     

Finite periodic structure approach to large scanning array problems

There are two conventional techniques dealing with mutual coupling problems for antenna arrays. The "element-by-element" method is useful for small to moderate size arrays. The "infinite periodic structure" method deals with one cell of infinite periodic structures, including all the mutual coupling effects. It cannot, however, include edge effects, current tapers, and nonuniform spacings. A new technique called the "finite periodic structure" method, is presented and applied to represent the active impedance of an array, it involves two operations. The first is to convert the discrete array problem into a series of continuous aperture problems by the use of Poisson's sum formula. The second is to use spatial Fourier transforms to represent the impedance in a form similar to the infinite periodic structure approach. The active impedance is then given by a convolution integral involving the infinite periodic structure solution and the Fourier transform of the equivalent aperture distribution of the current over the entire area of the array. The formulation is particularly useful for large finite arrays, and edge effects, current tapers, and nonuniform spacings can also be included in the general formulation. Although the general formulation is valid for both the free and forced modes of excitation, the forced excitation problem is discussed to illustrate the method.     

Antenna radiation characteristics with partially coherent illumination

The radiation characteristics of a partially coherent illuminated antenna are found for both a circular aperture and a linear antenna. The antenna illumination function is assumed to be Gaussian, and the phase structure function in the plane of the antenna is assumed to be of the formcr^{nu}, withnu = 1, 5/3, and 2. The beam broadening and reduction in gain in decibels are found to be of the formKb^{alpha}, whereKandalphaare functions of the antenna illumination and the "law" of the phase structure function, andbis a function of the "level" of the phase structure function.     

Polarization mode control of two-dimensional photonic crystal laser having a square lattice structure

We investigate in detail control methods of polarization mode in a two-dimensional square-lattice photonic crystal laser. In order to control the polarization mode using the square lattice, we investigate the eigenmode of the electromagnetic field against the possible symmetry groups of a square lattice. Both the electromagnetic field distributions of lasing oscillation mode and the band diagram are significantly influenced by the symmetry groups. In the case of the square lattice structure, symmetries "p1", "pm", "p2", and "pmm" are suitable for obtaining the unidirectional polarization mode. Among these symmetry groups, the symmetry group "pmm" is especially interesting considering the simplicity of the eigenmode of the electromagnetic field. In order to obtain the symmetry group "pmm", we deform the unit cell structure of a square lattice from circular to elliptical and investigate the properties of symmetry group "pmm" in detail. The elliptical ratio of the unit cell structure can modify the coupling balance of a lightwave propagating in two perpendicular in-plane directions and can control the eigen energy of each band edge.