旋转式硅微机械陀螺的研究

分析了旋转式硅微机械陀螺的工作原理,建立了该陀螺的数学模型,设计了其敏感结构,计算了陀螺振动元件三个轴向的转动惯量、弹性支撑梁扭转刚度、振动元件角振动阻尼系数等动力学参数,计算分析了陀螺的电容敏感特性。对制作的陀螺进行性能测试的结果表明,该陀螺利用旋转载体自身的旋转角速度作为驱动,从而说明敏感载体的俯仰(或横滚)角速度原理正确,并且理论和试验都说明,当载体自旋角速度不同时,陀螺输出信号的比例系数也不同。     

基于视觉的环形激光陀螺自动调腔系统

针对激光陀螺调腔,设计了一种基于视觉的自动调腔系统.采用基于统计的图像分析方法,对激光陀螺光学谐振腔中的光阑和光束进行定位.根据几何光学,分析了谐振腔中反射镜位置失调与光束偏移之间的关系,并设计了基于图像的闭环位置控制律,对反射镜的位置进行调整.实验表明,该系统能够完成对光阑和光束的自动识别,能够较好地实现激光陀螺的调腔.     

改进型陀螺经纬仪提高读数精度方法的研究

利用CCD把陀螺仪的光学信号转换为电信号,通过DSP处理器对信号进行处理,得出真北方位值,从而降低测量的读数误差、提高读数精度的目的,使仪器的精度由原来的30"提高到5"。     

滤波器耦合槽直径对其性能的影响仿真

采用高频结构模拟软件模拟1／4λ同轴型带通微波陶瓷滤波器结构,讨论了耦合槽直径对滤波器的性能如带宽、插损、带内波动、阻带抑制等的影响。结果表明,随着耦合槽直径的增大,滤波器中心频率、插入损耗和阻带抑制减小,3dB带宽增大。讨论结果表明,可通过调整滤波器耦合槽直径的大小,得到理想性能的介质滤波器。     

A Prototype Bandpass Sigma-Delta Modulator Employing Crystal Resonator

This paper describes an initial work on a second-order bandpass Sigma-delta modulator employing crystal resonator. The aim of this work is to explore the possibilities of realizing bandpass sigma-delta modulator using non-electronic resonators, such as micro-mechanical resonators. The initial study is based on crystal resonators as they have similar characteristics as the other types of resonator and are readily available. In order to obtain the desired loop transfer function, a compensation circuit is proposed to cancel the anti-resonance in the crystal resonator. The modulator chip is fabricated in a 0.6-μ m CMOS process. The bandpass noise shaping is demonstrated in the experiment with a 1- and 8-MHz crystal resonator, respectively. Yong Ping Xu graduated from Nanjing University, P.R. China in 1977. He received his Ph.D. from University of New South Wales (UNSW) Australia, in 1994. From 1978 to 1987, he was with Qingdao Semiconductor Research Institute, P.R.China, initially as an IC design engineer, and later the deputy R&D manager and the Director. From 1993 to 1995, he worked on an industry collaboration project with GEC Marconi, Sydney, Australia, at the same university, involved in design of sigma-delta ADCs. He was a lecturer at University of South Australia, Adelaide, Australia from 1996 to 1998. He has been with the Department of Electrical and Computer Engineering, National University of Singapore since June 1998 and is now an Associate Professor. His general research interests are in the areas of mixed-signal and RF integrated circuits, and integrated MEMS and sensing systems. He is a Senior Member of IEEE. Xiaofeng Wang was born in Shangqiu, China, in 1980. He received B.Eng. degree from Northwestern Polytechnical University, Xi'an, China, in 2000 and M. Eng. degree from National University of Singapore, Singapore, in 2003, both in electrical engineering. He is currently working toward the Ph.D. degree at Tufts University, Medford, USA. His research is on high speed ADC design. Wai Hoong Sun was born in Taiping, Malaysia in 1976. He received the B. App. Sc. (Honours) degree in electrical engineering from the University of Toronto, Canada in 1999. After graduating, he joined Sharp Electronics Singapore as an R&D Engineer where he was involved in FPGA and digital IC design of display related circuits. In 2001 and 2002, he did full time research in the National University of Singapore on bandpass sigma-delta modulators. During that period, he was also a Graduate Tutor in electronics for second year electrical and computer engineering students. He then joined Philips Electronics Singapore in 2002 as a Lead Engineer. He did board-level designs for LCD and plasma televisions. He was also development project leader for a project that was successful in bringing to the market a range of LCD and plasma televisions. Currently, he is a Hardware Architect where he is responsible for the system-level electrical design of the television board.     

High-Precision and High-Resolution Measurements of Thermal Diffusivity and Infrared Emissivity of Water–Methanol Mixtures Using a Pyroelectric Thermal Wave Resonator Cavity: Frequency-Scan Approach

The thermal diffusivity and effective infrared emissivity of water–methanol mixtureswere measured at atmospheric pressure and ambient temperature using a pyroelectric thermal-wave resonator cavity. The applied frequency-scan method allows keeping the cavity length fixed, which eliminates instrumental errors and substantially improves the precision and accuracy of the measurements. A theoretical model describing conduction and radiation heat transfer in the cavity was developed. The model predictions and the frequency-scan experimental data were compared, showing excellent agreement. The measurements were performed for methanol volume fractions of 0, 0.5, 1, 2, 5, 10, 20, 40, 75, and 100%. The fitted thermal diffusivity and effective emissivity vs. concentration results of the mixtures were compared to literature theoretical and experimental data. The maximum resolution of 0.5% by volume of methanol in water by means of the thermal-wave cavity method is the highest reported to date using thermophysical techniques. Semi-empirical expressions for the mixture thermal diffusivity and infrared emissivity as functions of methanol concentration have been introduced. The expression for infrared emissivity is consistent with the physical principle of detailed balance (Kirchhoff’s law). The expression for thermal diffusivity was found to describe the data satisfactorily over the entire methanol volume-fraction range.     

Defects and Transport in Langasite II: Donor-doped (La<Subscript>3</Subscript>Ga<Subscript>4.75</Subscript>Nb<Subscript>0.25</Subscript>SiO<Subscript>14</Subscript>)

The electrical conductivity of Nb doped langasite (La₃Ga_4.75Nb_0.25SiO₁₄) was examined as a function of temperature and oxygen partial pressure by complex impedance spectroscopy. A pO₂-independent regime was found at high pO₂ followed by a pO₂^{− 1/6} dependent regime at low pO₂. A defect model consistent with these results was derived in which the electron density n is fixed by the density of ionized Nb donors at high pO₂ and by the generation of oxygen vacancies at low pO₂. The temperature and oxygen partial pressure dependence of the electron density was obtained independently by thermoelectric power measurements. The Nb donor ionization energy was determined to be 1.52 ± 0.06 eV, confirming Nb to be a deep donor in langasite. By combining conductivity and thermoelectric power data, an expression for the electron mobility given by μ_e = 1.1× 10^{− 2}exp( ) was obtained. After evaluating the temperature dependent conductivity data under reducing conditions, in light of the defect model, a value for the reduction enthalpy (E_r = 6.57 ± 0.24 eV) was derived.     

机抖激光陀螺抖动随机噪声概率分布的x^2检验

运用x^2检验方法对机抖激光陀螺（RLG）抖动噪声幅度的概率芬布进行了假设检验，证明了本文所采用的随机噪声注入方法能够保证抖动幅度的随机变化服从高斯概率密度分布。     

Applications of a Dissipative Quartz Converter

The paper discusses dissipative quartz converters for monitoring the water contents of gases, liquids, and solids as well as for research on new materials, in which use is made of a quartz resonator and dielectric sensor.     

石英谐振式力传感器测试系统的设计

石英谐振式力传感器是一种输出为频率信号的数字式传感器。测试系统包括测量电路、测量控制软件和数据分析软件三部分 ,提供了一个集数据采集、检测、分析、处理为一体的测试系统。从工程实际出发 ,论述了该类传感器测试系统的开发与研究 ,并编制了相应的软件。