电磁兼容设计指南：PCB技术详解（第二版）

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《印刷电路板设计技术：EMC合规指南》第二版是Mark I. Montrose编著的一本专业手册，由IEEE Press出版于2000年。本书针对电子和电气工程师设计者，深入探讨了在电子产品设计过程中确保电磁兼容（EMC）的重要性和策略。随着电子设备的日益复杂和全球化，对电磁干扰（EMI）控制的需求不断增加，因此掌握PCB设计中实现EMC合规的技术变得至关重要。在本书中，作者详细介绍了以下关键知识点： 1. **基本概念**：章节首先介绍了EMC的基本原理，包括EMI产生、传播和接收的原理，以及EMC标准的全球适用性，如FCC、CE、RoHS等。 2. **PCB设计原则**：讲解了如何在设计阶段考虑EMC，包括布局、布线、接地和电源管理。这涉及到信号完整性、电源噪声抑制、过电压保护、以及辐射和传导路径的最小化。 3. **滤波和屏蔽**：介绍如何设计有效的滤波网络来减少电源线上的电磁噪声，以及使用金属层、地平面和分割网络来创建物理屏蔽，防止内部信号泄漏和外部干扰进入。 4. **阻抗控制**：讨论了在不同频率范围下如何控制信号和电源线路的特性阻抗，以减小反射和耦合效应。 5. **信号完整性分析**：涵盖了时序分析、眼图和信号质量检查，以确保高速信号传输的可靠性，并降低电磁干扰的影响。 6. **模拟和数字部分的隔离**：讲解了模拟与数字电路之间的隔离方法，如使用光耦合器、磁耦合器或专用隔离芯片，以防止互相干扰。 7. **EMC测试和验证**：提供了关于如何进行预认证测试、生产测试以及产品上市后的合规性维护的实用建议。 8. **案例研究和最佳实践**：书中包含多个实际项目案例，展示如何将理论知识应用到实践中，以及业界公认的优秀设计策略。《印刷电路板设计技术：EMC合规指南》第二版是一本全面的工具书，帮助设计者在面临日益严格的EMC法规挑战时，提升他们的设计技能和产品的合规性，从而避免法律问题和提高产品质量。无论是刚入门的新手还是经验丰富的工程师，都能从中受益匪浅。

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Table of Contents

Chapter 1

1.1: FUNDAMENTAL

DEFINITIONS

1.2: ELEMENTS OF THE

ELECTROMAGNETIC

ENVIRONMENT

1.3: NATURE OF

INTERFERENCE

1.4: REGULATORY

REQUIREMENTS—NORTH

MERIC

1.5: REGULATORY

REQUIREMENTS—

WORLDWIDE

1.6: STANDARDS

1.7: EMISSION

REQUIREMENTS

1.8: IMMUNITY

REQUIREMENTS

1.9: ADDITIONAL

REGULATORY

REQUIREMENTS—NORTH

MERIC

1.10: SUPPLEMENTAL

INFORMATION

REFERENCES

Chapter 1 - Introduction

Printed Circuit Board Design Techniques for EMC Compliance: A Handbook for Designers, Second Edition

by Mark I. Montrose

IEEE Press

Recommend this title?

1.3 NATURE OF INTERFERENCE

EMC is grouped into two categories: internal and external. The internal

category is the result of signal degradation along a transmission path,

including parasitic coupling between circuits in addition to field coupling

between internal subassemblies, such as a power supply to a disk drive.

Stated more specifically, the problems are signal losses and reflections

along the path, along with crosstalk between adjacent signal traces.

External problems are divided into emissions and immunity. Emissions

derive primarily from harmonics of clocks or other periodic signals.

Remedies concentrate on containing the periodic signal to as small an area

as possible, blocking parasitic coupling paths to the outside world.

Susceptibility to external influences, such as ESD or radio frequency

interference, is related initially to propagated fields that couple into I/O

lines, which then transfer to the inside of the unit, and secondarily to case

shielding. The principal recipients are high-speed transmission lines and

sensitive adjacent traces, particularly those terminated with edge-triggered

components.

There are five major considerations when performing EMC analysis on a

product or design [1].

Frequency

. Where in the frequency spectrum is the problem

observed?

Amplitude

. How strong is the source energy level, and how great is its

potential to cause harmful interference?

Time

. Is the problem continuous (periodic signals), or does it exist

only during certain cycles of operation (e.g., disk drive write operation

or network burst transmission)?

Impedance

. What is the impedance of both the source and receptor

units, and the impedance of the transfer mechanism between the

two?

Dimensions

. What are the physical dimensions of the emitting device

that cause emissions to occur? RF currents will produce

electromagnetic fields that will exit an enclosure through chassis leaks

that equal significant fractions of a wavelength or significant fractions

of a "rise-time distance." Trace lengths on a PCB have a direct

relationship as transmission paths for RF currents.

Whenever an EMI problem is approached, it is helpful to review this list

based on product application. Understanding these five items will clear up

much of the mystery of how EMI exists within a PCB. Applying these five

considerations teaches us that design techniques make sense in certain

contexts but not in others. For example, single-point grounding is excellent

when applied to low-frequency applications, but it is completely

inappropriate for radio frequency signals, which is where most of the EMI

problems occur. Many engineers blindly apply single-point grounding for all

product designs, without realizing that additional and more complex

problems are created using this grounding methodology.

When designing a PCB, we are concerned with current flow within the

assembly. Current is preferable to voltage for a simple reason: current

always travels around a closed-loop circuit following one or more paths. It

Personal account | University of Southern Queensland

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Table of Contents

Chapter 1

1.1: FUNDAMENTAL

DEFINITIONS

1.2: ELEMENTS OF THE

ELECTROMAGNETIC

ENVIRONMENT

1.3: NATURE OF

INTERFERENCE

1.4: REGULATORY

REQUIREMENTS—NORTH

AMERICA

1.5: REGULATORY

REQUIREMENTS—

WORLDWIDE

1.6: STANDARDS

1.7: EMISSION

REQUIREMENTS

1.8: IMMUNITY

REQUIREMENTS

1.9: ADDITIONAL

REGULATORY

REQUIREMENTS—NORTH

MERIC

1.10: SUPPLEMENTAL

INFORMATION

REFERENCES

Chapter 1 - Introduction

Printed Circuit Board Design Techniques for EMC Compliance: A Handbook for Designers, Second Edition

by Mark I. Montrose

IEEE Press

Recommend this title?

1.4 REGULATORY REQUIREMENTS—NORTH

AMERICA

Electrical and electronic products generate RF energy. Electromagnetic

emission levels are set by rules and regulations mandated by domestic and

international governments or agencies. In the United States, the Federal

Communications Commission (FCC) regulates the use of radio and wire

communications. The FCC is an independent government agency,

responsible for ensuring interstate and international communication by

radio, television, satellite, and cable.

In Canada, Industry Canada (IC) is the agency responsible for regulating

radio and wire communication. Industry Canada performs a function similar

to that of the Federal Communications Commission. Harmonized test

requirements and standards for North America exist between both the FCC

and IC.

The FCC regulates electronic products by specifying technical standards

and operational requirements through the Code of the Federal Register

(CFR), Title 47. The sections within 47CFR that are most applicable to

products discussed herein are Parts 2, 15, 18, and 68. These regulations,

developed over many years, are based on complaints filed with the

Commission. The most prominent FCC Parts are summarized in the

following list. In Canada, the specification equivalent to 47CFR, Part 15, is

SOR 88/475.

1. Part 2 is an administrative section that details aspects of how to

comply with 47CFR. Included are allocated frequency bands, radio

treaty matters, and general rules and regulations. The rules and

regulations include registration requirements, authorization

procedures, definitions, and various processes to ensure that the

federal code is properly administered.

2. Part 15 regulates products that generate unlicensed radio frequency

energy, both intentional and non-intentional. Information Technology

Equipment (ITE) falls within Part 15.

3. Part 18 regulates Industrial, Scientific, and Medical (ISM) equipment.

These devices use radio waves for proper operation.

4. Part 68 regulates electronic equipment connected to a telephone

network. This part provides a uniform standard for protecting the

telephone network from harm caused by connection of terminal

equipment.

The FCC defines a digital device as

An unintentional radiator (device or system) that generates and

uses timing signal or pulses at a rate in excess of 9,000 pulses

(cycles) per second and uses digital techniques; inclusive of

telephone equipment that uses digital techniques or any device or

system that generates and uses radio frequency energy for the

purpose of performing data processing functions, such as

electronic computations, operations, transformation, recording,

filing, sorting, storage, retrieval or transfer.

Digital computing products are classified into two categories: Class A and

B. The FCC and IC use the same definitions.

Personal account | University of Southern Queensland

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Table of Contents

Chapter 1

1.1: FUNDAMENTAL

DEFINITIONS

1.2: ELEMENTS OF THE

ELECTROMAGNETIC

ENVIRONMENT

1.3: NATURE OF

INTERFERENCE

1.4: REGULATORY

REQUIREMENTS—NORTH

MERIC

1.5: REGULATORY

REQUIREMENTS—

WORLDWIDE

1.6: STANDARDS

1.7: EMISSION

REQUIREMENTS

1.8: IMMUNITY

REQUIREMENTS

1.9: ADDITIONAL

REGULATORY

REQUIREMENTS—NORTH

MERIC

1.10: SUPPLEMENTAL

INFORMATION

REFERENCES

Chapter 1 - Introduction

Printed Circuit Board Design Techniques for EMC Compliance: A Handbook for Designers, Second Edition

by Mark I. Montrose

IEEE Press

Recommend this title?

1.5 REGULATORY REQUIREMENTS—WORLDWIDE

Test requirements, standards, and procedures have been harmonized on a

worldwide basis. The principles discussed herein will allow regulatory

compliance to be achieved with minimal development cost and shorter

design cycles. The harmonization process is based on the work of expert

technical committees reporting to the International Electrotechnical

Commission (IEC).

The IEC works closely with the International Standards Organization (ISO),

which is chartered by the United Nations. Many countries throughout the

world are members. The IEC oversees the work of technical committees

working on a particular product sector. The IEC's objectives are to

"promote international co-operation on all questions of standardization ...

achieved by issuing publications including recommendations in the form of

international standards."

Two IEC technical committees work on EMC standards. The first is TC77,

Electromagnetic compatibility between equipment including networks

. The

second committee is

International Special Committee on Radio

Interference

(Comité International Spécial des Perturbations

Radioélectriques or CISPR). CISPR publications deal primarily with limits

and measurements of the radio interference characteristics of potentially

disturbing sources or emissions. CISPR and IEC standards coexist to

define most technical aspects related to EMC compliance.

The IEC publications themselves have no legal requirements. National

committees do not have to adopt them, although several countries outside

of Europe have incorporated them into their national laws. The important

aspect of IEC standards is that they have been adopted and harmonized

as a European standard for all members of the European Union. Once

published as a harmonized document, a legal requirement now exists.

A separate organization, the Committee for European Electrotechnical

Standardization (Comité Européen de Normalisation Electrotechnique, or

CENELEC), is responsible for developing European standards for electrical

equipment. CENELEC received its charter from the Parliamentary

Commission of the European Union and produces EMC standards for use

with the EMC Directive, usually based on IEC and CISPR publications.

For telecommunications equipment, the European Telecommunications

Standards Institute, or ETSI, is the standards-making body. ETSI develops

standards for telecommunications network equipment not supplied to the

subscriber, in addition to radio communication equipment and broadcast

transmitters.

CENELEC and ETSI adopt IEC and CISPR publications, whenever

possible, as a basis for preparing a formal standard. The CENELEC

committee responsible for preparing EMC standards is TC110. Technical

Committee TC110 has several subcommittees, including SC110A, which is

responsible for immunity requirements of Information Technology

Equipment (ITE).

International EMC publications are commonly referred to as CISPR or IEC,

when in fact the real standard, after adoption and publication by the

European Commission, is prefixed with an EN (European Normalization)

number. To summarize, the European Commission adopts into law

requirements developed by CISPR and the IEC, as well as other European

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电磁兼容设计指南：PCB技术详解（第二版）

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Printed circuit board design techniques for EMC compliance

Printed Circuit Board Design Techniques for EMC Compliance, Second Edition

PCB Design Techniques for EMC Compliance

EMC on Printed Circuit Board

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PCB设计技术：实现EMC合规的指南

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