PCB 被动组件的隐藏特性解析 传统上，EMC一直被视为「黑色魔术（black magic）」。其实，EMC是可以藉由数学公式来理解的。不过，纵使有数学分析方法可以利用，但那些数学方程式对实际的EMC电路设计而言，仍然太过复杂了。幸运的是，在大多数的实务工作中，工程师并不需要完全理解那些复杂的数学公式和存在于EMC规范中的学理依据，只要藉由简单的数学模型，就能够明白要如何达到EMC的要求。本文藉由简单的数学公式和电磁理论，来说明在印刷电路板（PCB）上被动组件（passivecomponent）的隐藏行为和特性，这些都是工程师想让所设计的电子产品通过EMC标准时，事先所必须具备的基本知识。导线和PCB走线导线（wire）、走线（trace）、固定架……等看似不起眼的组件，却经常成为射频能量的最佳发射器（亦即，EMI的来源）。每一种组件都具有电感，这包含硅芯片的焊线（bond wire）、以及电阻、电容、电感的接脚。每根导线或走线都包含有隐藏的寄生电容和电感。这些寄生性组件会影响导线的阻抗大小，而且对频率很敏感。依据LC 的值（决定自共振频率）和PCB走线的长度，在某组件和PCB走线之间，可以产生自共振（self-resonance），因此，形成一根有效率的辐射天线。在低频时，导线大致上只具有电阻的特性。但在高频时，导线就具有电感的特性。因为变成高频后，会造成阻抗大小的变化，进而改变导线或PCB 走线与接地之间的EMC 设计，这时必需使用接地面（ground plane）和接地网格（ground grid）。导线和PCB 走线的最主要差别只在于，导线是圆形的，走线是长方形的。导线或走线的阻抗包含电阻R和感抗XL = 2πfL，在高频时，此阻抗定义为Z = R + j XL j2πfL，没有容抗Xc = 1/2πfC存在。频率高于100 kHz以上时，感抗大于电阻，此时导线或走线不再是低电阻的连接线，而是电感。一般而言，在音频以上工作的导线或走线应该视为电感，不能再看成电阻，而且可以是射频天线。
上传时间： 2013-11-16
上传用户：极客
国外游戏开发者杂志2003年第二期配套代码，包含了Jon Blow的交互工具的版本更新，使用了一个Kohonen Self-Organizing Feature Map来区分系统的行为
上传时间： 2014-01-19
上传用户：拔丝土豆
Abbrevia is a compression toolkit for Borland Delphi, C++Builder, & Kylix. It supports PKZIP 4, Microsoft CAB, TAR, & gzip formats & the creation of self-extracting archives. It includes visual components that simplify the manipulation of ZIP files.
标签： compression Abbrevia supports Borland
上传时间： 2014-01-13
上传用户：来茴
摘 : 通过使用 peer-to-peer(P2P)计算模式在 Internet 物理拓扑基础上建立一个称为 P2P 覆盖网络(P overlay network)的虚拟拓扑结构,有效地建立起一个基于 Internet 的完全分布式自组织网络路由模型 集中式自组织网络路由模型(hierarchical aggregation self-organizing network,简称 HASN).分别描述了 HASN 由模型的构建目标和体系结构,并详细分析了 HASN 采用的基于 P2P 计算模式的分布式命名 路由发现和更 算法 HASN_Scale,并在仿真实验的基础上,对 HASN 路由模型的性能进行了验证.
标签： peer-to-peer P2P Internet overlay
上传时间： 2014-01-21
上传用户：zhenyushaw
This book, the Sun™ ONE Message Queue (MQ) 3.0.1 Administrator’s Guide, provides the background and information needed to perform administration tasks for an MQ messaging system. This preface contains the following sections: • Audience for This Guide • Organization of This Guide • Conventions • Other Documentation Resources
标签： Administrator backgroun the provides
上传时间： 2014-10-28
上传用户：shawvi
This book provides information about the concepts and procedures needed by a developer of messaging applications in a Sun™ ONE Message Queue (MQ) environment. This preface contains the following sections: • Audience for This Guide • Organization of This Guide • Conventions • Other Documentation Resources
标签： information procedures developer messaging
上传时间： 2013-12-14
上传用户：netwolf
DIGITAL IMAGERY is pervasive in our world today. Consequently, standards for the efficient representation and interchange of digital images are essential. To date, some of the most successful still image compression standards have resulted from the ongoing work of the Joint Photographic Experts Group (JPEG). This group operates under the auspices of Joint Technical Committee 1, Subcommittee 29, Working Group 1 (JTC 1/SC 29/WG 1), a collaborative effort between the International Organization for Standardization (ISO) and International Telecommunication Union Standardization Sector (ITUT). Both the JPEG [1–3] and JPEG-LS [4–6] standards were born from the work of the JPEG committee. For the last few years, the JPEG committee has been working towards the establishment of a new standard known as JPEG 2000 (i.e., ISO/IEC 15444). The fruits of these labors are now coming to bear, as JPEG-2000 Part 1 (i.e., ISO/IEC 15444-1 [7]) has recently been approved as a new international standard.
标签： Consequently efficient pervasive standards
上传时间： 2013-12-21
上传用户：源弋弋
Microsoft Press books are available through booksellers and distributors worldwide. For further information about international editions, contact your local Microsoft Corporation office or contact Microsoft Press International directly at fax (425) 936-7329. Visit our Web site at www.microsoft.com/mspress. Send comments to mspinput@microsoft.com. Microsoft, Microsoft Press, Visual Basic, Visual Studio, Windows, and Windows NT are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Other product and company names mentioned herein may be the trademarks of their respective owners. The example companies, organizations, products, domain names, e-mail addresses, logos, people, places, and events depicted herein are fictitious. No association with any real company, organization, product, domain name, e-mail address, logo, person, place, or event is intended or should be inferred.
标签： distributors booksellers Microsoft available
上传时间： 2013-12-27
上传用户：wuyuying
％ This program calculates radar ranges in a jamming environment. It works ％ with both Stand-off jamming and self-screening jamming for steady and Swerling type ％ targets with frequency agility, coherent integration and standard atmosphere/rain ％ attenuation
标签： environment calculates Stand-off program
上传时间： 2013-12-24
上传用户：sammi
2005 Center for Biological & Computational Learning at MIT and MIT All rights reserved. Permission to copy and modify this data, software, and its documentation only for internal research use in your organization is hereby granted, provided that this notice is retained thereon and on all copies. This data and software should not be distributed to anyone outside of your organization without explicit written authorization by the author(s) and MIT.
标签： Computational Biological MIT Permissio
上传时间： 2014-01-27
上传用户：gaome
