一款紧凑增强型可变阻抗电磁带隙结构

基于传统AI-EBG结构,提出了一种小尺寸的增强型电磁带隙结构,实现了从0.5~9.4 GHz的宽频带-40 dB噪声抑制深度,且下截止频率减少到数百MHz,可有效抑制多层PCB板间地弹噪声。文中同时研究了EBG结构在高速电路应用时的信号完整性问题,使用差分信号方案可改善信号完整性。     

宽带DDS跳频源设计

直接数字合成（DDS）简单可靠、控制方便，具有很高的频率分辨率，高速转换，非常适合快速跳频的要求。在对DDS基本原理进行了简要介绍和分析后，提出宽带跳频源设计方案。     

Analysis of saltation characteristics of bed-load transport in flowing water

The study of bed-load transport is of great significance both in theory and in practice. This paper discusses the saltation of bed-load solid grains in flowing water. Experiments and theoretic analysis have been made by means of high-speed photographing and advanced data processing technique with a combined method based on mechanical and statistical theories. It indicates that the saltation is the main form of the bed-load transport under ordinary flowing conditions. In the meantime, taking successive saltation as the model of bed-load transport, systematic analysis has been made with regard to the kinematic properties and mechanism of saltation. The statistical analysis shows that the probability density functions of the relative height and length of saltation are in conformity with Γ-type distribution, while the probability density functions of the relative velocities of saltation are in conformity with the Gaussian distribution. The project supported by National Natural Science Foundation of China     

EPON:下一代接入网的最佳选择

EPON技术具有大带宽、高性价比、结构简单和一定服务质量保证等特点,被业界普遍看好,成为 下一代接入网的最佳候选技术.本文主要介绍了EPON的工作原理、分层结构、接入控制和组帧方式,最后给出 了实现EPON的关键技术和难点以及EPON的发展近况.     

Spatiotemporal and Thermal Analysis of VCSEL for Short-range Gigabit Optical Links

High-speed Optoelectronic Modules using Vertical Cavity Surface Emitting Lasers (VCSEL) coupled to Multi Mode Fibers (MMF) are a performing and low-cost solution for 10 Gigabit Ethernet (10 GbE) in short-distance optical links. A complete model of the spatiotemporal behavior of multimode VCSELs, through static and dynamic response, noise, thermal effects, and its coupling to MMF has been investigated. Relative Intensity Noise shows modal dependence and can be affected by spatial filtering due to coupling and fiber propagation. Simulations permit to evaluate critical parameters, such as modulation formats, launching conditions, and operating temperature for global bandwidth and eye diagram optimization up to 10 Gb/s. Simulation results are compared to measurements on prototype optoelectronic modules.     

基于5G-R系统的高铁站台场景信道特性

为推进智能铁路总体建设,实现高速铁路智能化,高铁信息基础设施将应用第五代移动通信技术(5G)建设铁路5G专用移动通信系统,2.1 GHz有望成为铁路5G专用移动通信系统的承载频段。高铁站台作为客货乘降与调度中转的功能核心,其在2.1 GHz下的电波传播特性亟待研究。本文以厦门北站高铁站台为研究场景,利用射线跟踪(RT)技术仿真2.1 GHz频段下的电波传播,基于仿真结果分析此场景无线信道特性,包括均方根时延扩展(RMS DS)、到达/离开方位角扩展、到达/离开俯仰角扩展(ASA/ASD, ESA/ESD)、交叉极化比(XPR)和以上参数的互相关。根据以上结果,对高铁站台场景中铁路5G专用移动通信系统的设计和评估提出相关建议。     

Solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes under high-speed vibration milling

The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C₆₀(CH₂N(CH₃)CHR), R=H (4a), C₆H₅ (4b), p-NO₂-C₆H₄ (4c), p-CH₃O-C₆H₄ (4d), p-(CH₃)₂N-C₆H₄ (4e)) were obtained in moderate yields from reactions of C₆₀ with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C₆₀ with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C₇₀ with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines.     

爆轰试验中高速摄影控制及闪光装置改进

研究爆轰试验高速摄影中,闪光灯和摄影机快门失灵引起试验失败问题,提出对试验操控装置和闪光灯电源改进措施。首先,在实验操控上增加防止仅雷管起爆的逻辑控制,并采用集中控制,分布检测设计;其次,在闪光氙灯电源中,采用伪火花开关和多节LC（电感-电容）脉冲形成线技术,解决氙灯存在的自闪、不引燃和光强不均。此外,还解决了装置研制中遇到的电磁干扰、同步引燃等问题。通过改进,有效地防止了爆轰试验中高速摄影光学影像丢失情况和底片曝光不均匀现象,介绍了主要元件、线路和系统、实验结果及研制过程。     

气泡高速摄影和载荷测试技术综述

气泡运动学和动力学一直为流体力学研究热点之一. 近年来,高速摄影技术和气泡载荷测试设备发展迅速,为人们研究气泡行为和载荷分析提供了强有力的支持. 本文综述高速摄影和载荷测试技术在气泡动力学中的应用与发展. 首先,简要回顾气泡现象的成因和分类;其次,详述高速摄影技术在捕获气泡形态中的应用;再次,回顾和讨论了气泡载荷测试设备以及试验手段的发展;最后,在上述基础上提出了一些尚需进一步完善的问题.     

12bit 800MSPS电流舵结构的高速DAC设计

本文设计了一个分辨率为12位，采样频率为800MHz的高速电流舵结构DAC。该设计基于TSMC0．18umCMOS工艺，采用了二进制码控制和温度计码译码控制相结合的方式，从而在降低DNL误差和减小毛刺的同时，又能实现较小的芯片面积和功耗。为达到高的精度和高的转换速度，该设计在系统结构、电路结构以及芯片版图等方面都做了优化。