4.EMI-Couplng Interactn Ok

7/29/2019 4.EMI-Couplng Interactn Ok

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ElectromagneticInteraction & Couplings


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The Electromagnetic EnvironmentThe Electromagnetic Environment


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EMI Categories


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Interference Fully opposed

Fully opposed signal


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Interference Partially opposed

Partially opposed signal


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EM Interaction & Coupling


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EM Interaction & Coupling


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EM Interaction Process

External Interaction - The EM wave couples with thesurface of the structure and causes electrical charge to flow

on the surface.

Resulting in a surface current density, and a charge

density which correspond to tangential H field andnormal E fields respectively.

Internal Interaction - The energy penetrates

(into)through the shell or envelope of the structure.

The penetration occurs because of apertures, antennas,exposed cables or other conductors, seams and joints in thepanels, or diffusion through the skin of the structure.


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Internal Propagation - Once the energy

penetrates into the interior, it will be propagated

most efficiently by the internal cables, which form

multiconductor transmission lines along which

energy is transported.

This energy is ultimately carried to the components, which

can be either temporarily upset or permanently damaged.


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Current and Charge at

the Device

Internal Charge &

Current responses

Internal E & H Field

Responses

Barrier Penetration

External Charge &

Current Responses

Conducted

ResponsesE & H

Field Response

External E & H FieldsExternal Source

External

Coupling

Conductive

Penetration

Aperture

Penetration

Diffusive

(spread)

Penetration

Interior

Fields

Internal

Coupling

Component Responses


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The Interaction Process

Cur r ent I nject ionCoupling t oConduct ors

Conduct orPenet r at ion

Aper t urePenet r at ion

Dif fusivePenet r at ion

Pulse PowerPr oduct ion

Wavef or mShaping

I nt er nalEquipmentExcita t ion

EM FieldRadiat ion f r om

Ant enna

EM I nt er actionwit h Syst em

Ext er ior

EM FieldCoupling t o

I nt er nal Conduct or s

I nt er nalConduct or

Pr opagat ion

PENE

RE


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LRDE

EM Interaction Depends on

Characteristics of Wave

Characteristics of System

Characteristics of propagating media

Structures in the vicinity of the system


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Mechanisms of interaction of

electromagnetic radiation with materials

Reflection

Absorption

Multiple reflection


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2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning

is a trademark used herein under license.


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The attenuation in decibels (dB) is defined as

Attenuation (dB) = 20 log10 (Ei/E),

where Ei is the incident field and E is the

transmitted or reflected field. Note that Ei > E.


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ReflectionMainly due to interaction of

electromagnetic radiation with the

electrons in the solid


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Skin EffectPhenomenon in which high frequency

electromagnetic radiation interacts

with only the near surface region ofan electrical conductor


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,

1

f

where f= frequency,

= magnetic permeability = 0r,

r= relative magnetic permeability,0 = 4 x 10

-7 H/m, and

= electrical conductivity in -1m-1.

Skin depth ()


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Absorption

Due to interaction of electromagneticradiation with the electric/magnetic

dipoles, electrons and phonons in the

solid


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EM COUPLING


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EM Coupling

Radiative,

Conductive,

Inductive

Capacitive


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LRDE

Distant EMI Source

E & H Field on Structure

Capacitive

Coupling

Inductive

Coupling

Radiative

Coupling

Conductive

Coupling

Induced Current & Charge

External Coupling ProcessExternal Coupling Process


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Methods of Coupling

Transfer Mechanism

Conductive

Electromagnetic

Magnetic Field

Electric Field

Coupling Direct radiation From Source to

Receptor

Radiated From Source &transferred to AC/Signal/control

cables

RF energy radiated by Cables

RF energy conducted by common

electrical supply


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Coupling Mechanism (system level)

System

A

System

BSystem

A

SystemB

Galvanic Coupling

(conductive Coupling)Capacitive Coupling

(E-Field Coupling)System

A

System

B

Mutual inductance

Mutual inductance

(Magnetic Coupling)

Stray cap

System

ASystem

B

Radiation

Radiation Coupling

Supply


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Trace to trace coupling within a PCB Structure

EMI Ch t i ti


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EMI Characterization

EMISSION:

It is a phenomenonthrough which a

system gives away

EM energy to its

environment

SUSCEPTIBILITY:

It is the phenomenonthrough which a

system gets in EM

energy from its

environment

SYSTEM

EMITTER

SUSCEPTOR


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Elements of an EMI Situation

Source "Culprit"

Coupling method "Path"

Sensitive device "Victim"

SOURCE PATH

VICTIM


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How Does EMI Affect Electronics?

Radiated and conducted interference

A. Conducted Interference Enters and Exits Equipment through

Wiring and Cabling

B. Radiated Interference Enters and Exits Equipment through

Wiring and Enclosure Penetration

Radiated Susceptibility Radiated Emissions

Conducted Susceptibility Conducted Emissions


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Radiated Coupling Field to Cable

Patient Monitor

Loop AreaInduced Current

Electromagnetic WaveRadio

VCM


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Interference to TV Reception

Two Interfering Signals Injected into TV

No Interference


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Transients

Electrostatic Discharge & Transient Pulses

ESD can induce glitches in circuits, leading to false triggering,

errors in address & data lines and latch-up of devices

Upset Damage

Degradation leading to future failure(s)


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PERSONAL COMPUTERS & PERIPHERALS,

RADIO RECEIVERS

Method #1Test at Approved Laboratory

Test Product at

approved

Laboratory

Report with

Technical

Information

Declaration of

ConformitySell Product

Declaration of Conformity. Does not go to the FCC


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RADIO TRANSMITTERS

ExamplesCordless Phones, Radio Transmitters, CB Radios, Wireless Products

CERTIFICATION:

Test ProductReport with

Technical

Information

Send Report and

Application to

FCC or TCB

FCC GRANT

with FCC ID Number

Sell Product


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CONDUCTED EMISSIONS TESTING

Measure Noise on Power Line

Spectrum Analyzer

Product

PowerCord


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RADIATED EMISSIONS TESTING

Test Site: Measure Radiated

Noise from Equipment Case

and Cables

Measuring Antenna

Product

3 m or 10 m

SpectrumAnalyzer

Open Area Test Site

Turntable


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RADIATED EMISSIONS TESTING

Test Site: Measure Radiated

Noise from Equipment Case

and Cables

Measuring Antenna

Product

3 m or 10 m

Photos: EMC Test System, Austin, TX emctest.com

SpectrumAnalyzer

Open Area Test Site

Turntable


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Typical Ambient Profile

Switching noise

Cell phone

FM Radio


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Immunity Test Requirements 1000-4 Series

IEC 61000-4-1: Introduction

IEC 61000-4- 2: Electrostatic Discharge Requirements

IEC 61000-4- 3: Radiated Immunity

IEC 61000-4- 4: Electrical Fast Transient IEC 61000-4- 5: Surge

IEC 61000-4- 6: Conducted RF Immunity

IEC 61000-4-7: Interharmonics

IEC 61000-4-8 & 9: Magnetic field immunity

IEC 61000-4-10: Damped Oscillatory pulsed field immunity

IEC 61000-4-11: Dips & Interrupts (power quality)

IEC 61000-4-12: Damped Oscillatory (surge)


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ESD Testing

ESD Simulator


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Anechoic Chamber

www.emctest.com


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Surge Coupling

Lightning and pulse sources cause high-

energy transients into power and data cables

IndirectDirect


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Voltage Dips & Interrupts

IEC 1000-4-11 Simulates brownouts and blackouts on equipment

operation

Voltage Dip:

Voltage Interrupt:

4.EMI-Couplng Interactn Ok

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