大功率GaInP/AlGaInP半导体激光器

制备了大功率实折射率GaInP/AlGaInP压应变分别限制量子阱激光器.所用外延材料在15°偏角的GaAs衬底上由有机金属气相外延一次外延生长得到.制备的激光器具有双沟脊波导结构,条宽和腔长分别为3和900μm,前后端面分别蒸镀5%的增透膜和95%的高反膜.分析了室温连续激射时激光器的光电输出性能.阈值电流的典型值为32mA,光学灾变阈值为88mW,功率为80mW时的工作电流为110mA,斜率效率为1W/A,串联电阻为3Ω.基横模光输出功率可达60mW,60mW时的平行结和垂直结的远场发散角分别为10°和32°,激射波长为658.4nm.器件的内损耗为4.1cm-1,内量子效率达80%,透明电流密度为648A/cm2.     

SET/CMOS hybrid process and multiband filtering circuits

We have developed an integration technology for the single electron transistor (SET)/CMOS hybrid systems. SET and CMOS transistors can be optimized without any possible degradation due to mixing dissimilar devices by adopting just one extra mask step for the separate gate oxidation (SGOX). We have confirmed that discrete devices show ideal characteristics required for the SET/CMOS hybrid systems. An SET shows obvious Coulomb oscillations with a 200-mV period and CMOS transistors show high voltage gain. Based on the hybrid process, new hybrid circuits, called periodic multiband filters, are proposed and successfully implemented. The new filter is designed to perform a filtering operation according to the periodic multiple blocking bands of which a period is originated from the SET. Such a novel function was implemented efficiently with a few transistors by making full use of the periodic nature of SET characteristics.     

Pulse stabilisation in harmonically FM modelocked erbium fibre ring laser with DFBLD

A new pulse stabilisation scheme for a harmonically frequency modulated (FM) modelocked erbium fibre ring laser using a distributed feedback laser diode (DFBLD) is presented. More than 65 dB supermode noise suppression in the RF spectrum was obtained with the proposed method. Effective reduction of supermode noise can be accomplished as the DFBLD in the fibre laser acts not only as a fast-gain saturated medium but also as an optical bandpass filter for suppressing supermode noise in a harmonically modelocked laser system.     

Measurements of coupling and reflection characteristics of butt-joints in passive waveguide integrated laser diodes

Amplified spontaneous emission (ASE) spectra of passive waveguide integrated lasers have been studied to estimate the coupling efficiency and the reflectivity at the butt-joints between active and passive waveguides. A new method has been proposed for the analysis of ASE to extract the coupling efficiency and reflectivity at the butt-joints. This method was applied experimentally to estimate the coupling and reflection of the passive waveguide integrated lasers with different amounts of vertical misalignments of active and passive waveguides.     

Multi-antenna scheme for high capacity transmission in the digital audio broadcasting

In this paper, we apply multi-antenna scheme to DAB system for high-rate transmission. In the MIMO-DAB system with a number of transmitting and receiving antennas increases the transmission rate efficiently with low multiplication operations. For channel estimation in the MIMO-DAB system, we propose a new PRS structure and evaluate the channel estimation performance. The proposed PRS structure can estimate multi-channel information based on the semi-blind processing. The performance of proposed PRS is compared with that of conventional training sequence employing Tarokh's transmission matrix. And also we investigate the performance limitation due to the imperfect channel estimation in a MIMO-DAB receiver. It has been shown that the MIMO-DAB system with multi-antennas can achieve the high-rate transmission for multimedia broadcasting and the performance of MIMO-DAB system is impaired by imperfect channel information.     

激光大气雷达系统中重合系数的计算

为了满足探测的目的,有效获取和反演雷达数据,需要对激光雷达系统的参数进行设计。给出了激光大气雷达系统中重合系数(几何因子)的计算方法,并且结合我校现有的激光大气雷达系统的技术参数,从对0～3km的气溶胶后向散射回波的有效探测出发,讨论了系统参数对重合系数的影响和利用改变系统参数的方法改变重合系数,以实现对激光雷达系统优化设计的可行性。计算和分析表明,该方法简单、直观、有效。     

3m法半电波暗室改造施工案例

介绍了北京交通大学3m法半电波暗室改造施工过程中遇到的问题、解决方案以及在暗室施工中应注意的各种事项.     

VoIP在美国的发展及对网络结构的影响

从美国发展网络电话的现状出发，介绍了网络电话的优缺点及其发展趋势．分析了网络电话对网络结构的影响。     

Robotic system approach for complete denture manufacturing

A robotic system for complete denture manufacturing, which can realize automatic implanting of artificial teeth, is described. The tooth arrangement algorithm is presented, including the equations of jaw-arch curve and teeth-arch curve, setup of a single tooth coordinate system and calculation of tooth position in teeth-arch curve. An expert system software is developed that integrates high-level dentist experiences and dexterous technician skills. Three-dimensional (3-D) display of tooth arrangement, human-computer interactive adjustment of tooth position and orientation in teeth-arch curve are achieved. Robot path planning and control data creation are realized by this software also. Finally, an experiment of complete denture manufacturing is made for a patient, a pair of complete dentures is obtained, and the results are analyzed. This robotic system is expected to change the manner of complete denture manufacturing wholly, and significantly improve product quality and manufacturing efficiency.     

现场总线通信控制专用芯片FF-H1研究与开发

本文介绍了FF-H1现场总线通信控制器专用芯片的系统体系结构、工作原理和设计实现.该芯片实现了IEC11582-2/ISA-S50.02物理层和IEC数据链路层底层协议规范,采用0.35微米CMOS工艺设计.下一步将在目前设计的基础上开发基于ARM AMBA总线体系结构的现场总线通信与控制系统芯片的通信控制器IP固核.