PCB 被動組件的隱藏特性解析 傳統(tǒng)上，EMC一直被視為「黑色魔術(shù)（black magic）」。其實(shí)，EMC是可以藉由數(shù)學(xué)公式來理解的。不過，縱使有數(shù)學(xué)分析方法可以利用，但那些數(shù)學(xué)方程式對實(shí)際的EMC電路設(shè)計而言，仍然太過復(fù)雜了。幸運(yùn)的是，在大多數(shù)的實(shí)務(wù)工作中，工程師并不需要完全理解那些復(fù)雜的數(shù)學(xué)公式和存在于EMC規(guī)范中的學(xué)理依據(jù)，只要藉由簡單的數(shù)學(xué)模型，就能夠明白要如何達(dá)到EMC的要求。本文藉由簡單的數(shù)學(xué)公式和電磁理論，來說明在印刷電路板（PCB）上被動組件（passivecomponent）的隱藏行為和特性，這些都是工程師想讓所設(shè)計的電子產(chǎn)品通過EMC標(biāo)準(zhǔn)時，事先所必須具備的基本知識。導(dǎo)線和PCB走線導(dǎo)線（wire）、走線（trace）、固定架……等看似不起眼的組件，卻經(jīng)常成為射頻能量的最佳發(fā)射器（亦即，EMI的來源）。每一種組件都具有電感，這包含硅芯片的焊線（bond wire）、以及電阻、電容、電感的接腳。每根導(dǎo)線或走線都包含有隱藏的寄生電容和電感。這些寄生性組件會影響導(dǎo)線的阻抗大小，而且對頻率很敏感。依據(jù)LC 的值（決定自共振頻率）和PCB走線的長度，在某組件和PCB走線之間，可以產(chǎn)生自共振（self-resonance），因此，形成一根有效率的輻射天線。在低頻時，導(dǎo)線大致上只具有電阻的特性。但在高頻時，導(dǎo)線就具有電感的特性。因為變成高頻后，會造成阻抗大小的變化，進(jìn)而改變導(dǎo)線或PCB 走線與接地之間的EMC 設(shè)計，這時必需使用接地面（ground plane）和接地網(wǎng)格（ground grid）。導(dǎo)線和PCB 走線的最主要差別只在于，導(dǎo)線是圓形的，走線是長方形的。導(dǎo)線或走線的阻抗包含電阻R和感抗XL = 2πfL，在高頻時，此阻抗定義為Z = R + j XL j2πfL，沒有容抗Xc = 1/2πfC存在。頻率高于100 kHz以上時，感抗大于電阻，此時導(dǎo)線或走線不再是低電阻的連接線，而是電感。一般而言，在音頻以上工作的導(dǎo)線或走線應(yīng)該視為電感，不能再看成電阻，而且可以是射頻天線。
上傳時間： 2013-11-16
上傳用戶：極客
國外游戲開發(fā)者雜志2003年第二期配套代碼，包含了Jon Blow的交互工具的版本更新，使用了一個Kohonen Self-Organizing Feature Map來區(qū)分系統(tǒng)的行為
上傳時間： 2014-01-19
上傳用戶：拔絲土豆
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.
標(biāo)簽： compression Abbrevia supports Borland
上傳時間： 2014-01-13
上傳用戶：來茴
摘 : 通過使用 peer-to-peer(P2P)計算模式在 Internet 物理拓?fù)浠A(chǔ)上建立一個稱為 P2P 覆蓋網(wǎng)絡(luò)(P overlay network)的虛擬拓?fù)浣Y(jié)構(gòu),有效地建立起一個基于 Internet 的完全分布式自組織網(wǎng)絡(luò)路由模型 集中式自組織網(wǎng)絡(luò)路由模型(hierarchical aggregation self-organizing network,簡稱 HASN).分別描述了 HASN 由模型的構(gòu)建目標(biāo)和體系結(jié)構(gòu),并詳細(xì)分析了 HASN 采用的基于 P2P 計算模式的分布式命名 路由發(fā)現(xiàn)和更 算法 HASN_Scale,并在仿真實(shí)驗的基礎(chǔ)上,對 HASN 路由模型的性能進(jìn)行了驗證.
標(biāo)簽： peer-to-peer P2P Internet overlay
上傳時間： 2014-01-21
上傳用戶：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
標(biāo)簽： Administrator backgroun the provides
上傳時間： 2014-10-28
上傳用戶：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
標(biāo)簽： information procedures developer messaging
上傳時間： 2013-12-14
上傳用戶：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.
標(biāo)簽： Consequently efficient pervasive standards
上傳時間： 2013-12-21
上傳用戶：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.
標(biāo)簽： distributors booksellers Microsoft available
上傳時間： 2013-12-27
上傳用戶：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
標(biāo)簽： environment calculates Stand-off program
上傳時間： 2013-12-24
上傳用戶：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.
標(biāo)簽： Computational Biological MIT Permissio
上傳時間： 2014-01-27
上傳用戶：gaome
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