针对电容型MEMS读出电路噪声与失调的优化

This paper presents a high precision CMOS readout circuit for a capacitive MEMS gyroscope. A continuous time topology is employed as well as the chopper noise cancelling technique. A detailed analysis of the noise and mismatch of the capacitive readout circuit is given. The analysis and measurement results have shown that thermal noise dominates in the proposed circuit, and several approaches should be used for both noise and mismatch optimization. The circuit chip operates under a single 5 V supply, and has a measured capacitance resolution of 0.2 aF/√Hz. With such a readout circuit, the gyroscope can accurately measure the angular rate with a sensitivity of 15.3 mV/°/s.     

用MOCVD方法在GaAs衬底上低温生长ZnO薄膜

采用二乙基锌(DEZn)和水(H2O)作为生长源,利用金属有机化学气相沉积(MOCVD)的方法,在100～400℃低温范围内,在GaAs(001)衬底上制备了ZnO薄膜.利用X射线衍射(XRD),室温PL,AFM,SEM研究了薄膜的晶体结构特性、发光特性及表面形貌特性.XRD分析表明ZnO薄膜具有很强的c轴取向,(002)峰的FWHM平均值为0.3°.当生长温度达到400℃时从SEM测量结果可以观察到薄膜表面呈六角状结晶.随着生长温度的升高,薄膜的晶粒尺寸变大,结晶质量得到提高但同时表面变粗糙.室温PL测量显示薄膜在370nm附近有强的近带边发射,没有观测到深能级发射峰.     

A high precision CMOS weak current readout circuit

rents from 1 pA to 300 nA can be detected with a maximum nonlinearity of 0.3% over the full scale.     

Performance analysis of microcell/macrocell with reuse partitioning in TDMA‐based cellular systems

System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two‐tier TDMA‐based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA–FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one‐tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

一种雷达通信一体化方法

提出了一种基于步进变频信号的雷达通信一体化系统,设计了一种融合雷达信号和通信信息的一体化信号,并对不同雷达之间的同步和数据处理流程进行了分析。仿真结果表明,这种一体化共享信号的调制解调方法是可行的,可在对雷达性能影响较小的前提下实现二进制数据的准确传送,具有较低的误码率。不同雷达可以在实现粗略同步的情况下进行通信和测距。     

Ba_5(Nb_(1-x)Sb_x)_4O_(15)微波介电陶瓷的低温烧结

添加质量分数为1%的H3BO3为助烧剂。研究了Ba5(Nb1–xSbx)4O15(0≤x≤0.2)陶瓷的烧结特性、显微结构和微波介电性能。结果表明:当x≤0.15时,该类陶瓷可在900℃附近烧结,并伴有少量BaSb2O6和BaB2O4相;随着x从0增加到0.2,εr和τf均有较大幅度下降;Q.f先升后降。在900℃烧成温度下,x为0.15的陶瓷获得较好的微波介电性能:εr为29.21,Q.f为13 266 GHz,τf为11×10–6℃–1,并能与Ag电极很好相容,基本满足LTCC工艺的要求。     

纳米二氧化锰的超电容特性研究

利用化学混合法制备了非晶二氧化锰/导电碳黑复合材料,比表面积达168.40m2/g,一次粒子粒径达100nm以下,显示出良好的电容特性,单电极比容可达410F/g。以活性炭作负极组装成电容器,工作电位窗达1.6V,比容量可达35F/g以上,且电容器经500次充放电循环后容量衰减不到5%。     

一种被动式时间同步算法的研究与设计

随着网络技术的不断发展，许多网络应用对网络中各个节点的时钟同步有着很高的要求。详细讨论了被动式同步算法的思想，提出了基于被动式同步算法的延时误差调节方案。方案有效降低了授时误差，同时改善了客户时钟的频率性能。     

液晶光阀的双稳态特性研究

测量了TB3639型液晶光阀在电压驱动下的光谱特性及其光学双稳态特性,并讨论其产生光学双稳态特性的非线性效应物理机制,分析了液晶光阀的光学双稳态特性不明显的原因.分析结果表明,扭曲角对液晶光阀的光学双稳态特性影响较大,由于TN型液晶光阀的扭曲角只有90°,导致其双稳态特性不是很明显,TB3639型液晶光阀在某一电压范围内存在光学双稳态特性.     

通孔氧化铝模板的制备和光学特性

采用阳极氧化法,制备了二维有序纳米通孔氧化铝模板.研究了工艺参数对通孔有序性、孔径、模板厚度等的影响,测量了通孔氧化铝模板的光透过、光吸收和光发射等光学特性.结果表明,在波长360 nm附近通孔氧化铝模板的光透过谱线和光吸收谱线发生突变,波长大于360 nm时,光透过增强;波长小于360 nm时,光吸收增强.通孔氧化铝模板的光致发光强度和峰位与激发光波长有关,光致发光谱范围在340～600 nm.