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AN INTRODUCTION TO
ELECTROMAGNETIC
COMPATIBILITY (EMC)PRESENTED BY
DR. WILLIAM G. DUFF
Applied Technology Institute 349 Berkshire Drive Riva, Maryland 21140 888-501-2100/410-956-8805 Website: www.ATIcourses.com Email: ATI@ATIcourses.com
ATI Course Schedule: http://www.ATIcourses.com/schedule.htm ATI’s Introduction To EMI : http://www.aticourses.com/sampler/Intro_to_EMI.pdf
www.ATIcourses.com
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INTRODUCTION TO EMC DAY 1 SYLLABUS
Examples of EMI Elements of EMI Definition of Terms and Units Types of EMI Sources of EMI Propagation and Coupling Victims of EMI EMC in Wireless Systems
INTRODUCTION TO EMCDAY 2 SYLLABUS
EMI in Equipments and Systems EMI Coupling Modes Common Mode Coupling Differential Mode Coupling Common Impedance Ground Loop Grounding EMI Mitigation Filters, Ferrities, etc.
INTRODUCTION TO EMCDAY 3 SYLLABUS
Electromagnetic Shielding Shielding Applications Characteristics of Electromagnetic Fields Reflection Absorption Shielding Compromises Shielding Cables Design for EMC EMI Diagnostics and Fixes EMI Specifications and Standards
INTRODUCTION TO EMC DAY 1
Examples of EMI
What is EMI?
• RFI = Radio Frequency Interference
• TVI = Television Interference• Radio Noise• Electrical Noise• Transient Disturbances• Electromagnetic Pollution• Surges and Sags• Ground Bounce• Crosstalk• Corona and Arcing• Sparking• Electrostatic Discharges• Lightning Discharges
EMI = Electromagnetic Interference, Alias:• Relay Chatter• Noise Immunity Level• Audio Hum• Shot Noise• Flicker Noise• White Noise• Thermal Noise• Johnson Noise• TV Snow• Hum Bars• Motorboating• Degenerative Feedback• Hiss, Buzz and Hum• Screen Flicker
E3 = Electromagnetic Environmental Effects
EME = Electromagnetic EnvironmentEMC = Electromagnetic CompatibilityEMI = Electromagnetic InterferenceEMP = Electromagnetic PulseESD = Electrostatic DischargeHEMP = High Altitude EMP
HERF = Hazards of EM Radiation to FlightHERF = Hazards of EM Radiation to FuelHERO = Hazards of EM Radiation to OrdnanceHIRF = High Intensity Radiated FieldsHPM = High Power MicrowaveRADHAZ = Radiation HazardsRFI = Radio Frequency Interference
Historical EMI/E3-Related Incidents
Operation Restore Democracy (Haiti-1995)• Air wings of USS America & USS Eisenhower
replaced with men & helicopters of 10th Infantry Div. and 75th Ranger Regiment.
• Army aircraft not designed or tested for carrier operation, carriers required to turn off almost all communications and radar surveillance systems.
Pershing II Nuclear Missile (Germany)• Missile motor exploded during routine
maintenance• Electrostatic discharge identified as the
cause• 3 dead
Blackhawk Helicopter (Germany and USA - 1987)• Several potentially fatal incidents and a fatal crash• Suspected cause was interference from high
power radio transmitters• Entire fleet grounded for 3 months during
investigation• Extensive test and retrofit program necessary
USS Forrestal (Vietnam -1969)• ZUNI rocket inadvertently launched by a ship radar • 134 dead• 27 aircraft destroyed• $72M damage to ship ($335M in 2000 dollars)• Largest Naval loss of life since WW II
HMS Sheffield (Falkland Islands -1982)• Hit by undetected EXOCET missile• EMI caused degradation of surveillance
radar• 21 dead, • Ship sank 4 days later
Courtesy of Jose Reza
EMI CASE HISTORIES
• Blackhawk Helicopter• Aircraft Flight Controls• Automobile Electronics• Ship Propulsion System• Medical Electronics• Office Electronics• Consumer Electronics • Process Control
Proper Grounding and/or Shielding May Have Avoided May Have Avoided
Some of These ProblemsSome of These Problems
ELECTROMAGNETIC ENVIRONMENT EFFECTS (E3)
Performance degradation of receiver signal processing circuits
Erroneous or inadvertent operation of electromechanical equipments, electronic circuits, components, ordnance, etc.
Burnout or voltage breakdown of components, antennas, etc.
Unintentional denotation or ignition of electroexplosive devices, flammable materials, etc.
Personnel Injuries
ELECTROMAGNETIC ENVIRONMENT EFFECTS (E3) CONTINUED
POTENTIAL EMI INTERACTIONS
Interactions between on board equipments Interactions between on board equipments and
the electromagnetic environment Interactions between on board equipments and
test equipments
INTRODUCTION TO EMC DAY 1
Elements of EMI
ELEMENTS OF EMIELEMENTS OF EMI
SOURCESOF EMI COUPLING VICTIM OF
EMI
EMI CULPRIT AND VICTIMEMI CULPRIT AND VICTIM
EMISource
SignalSource
SignalReceiver
CULPRIT
VICTIM
COUPLING PATH
CONDUCTED OR RADIATEDCONDUCTED OR RADIATED COUPLING COUPLING
SOURCE COUPLING VICTIM
EMI SOURCES
TRANSMITTERSCOMPUTER CLOCKSELECTRIC MOTORS
SWITCHES AND RELAYSLIGHTNING
ELECTROSTATIC DISCHARGE
EMI COUPLING
CONDUCTED
Power Lines
Interconnecting Signal Cables
Common GroundImpedance
RADIATED
Antenna-to-AntennaCase Radiation
Case PenetrationField-to-WireWire-to-FieldWire-to-Wire
EMI VICTIMS
RECEIVERSANALOG SENSORS
ANALOG AMPLIFIERSCONTROL SYSTEMS
COMPUTERSORDNANCEPERSONNEL
PRIMARY EMI INTERACTIONSEMI SOURCE(EMITTER)
PRIMARY COUPLINGMECHANISM
EMI VICTIM(RECEPTOR)
RADIATEDANT-ANT
RECEIVERS
TRANSMITTERSRADIATED
ANT-CABLEANT-CASE
ELECTRONICEQUIPMENT
RADIATEDCABLE-ANTCASE-ANT
RECEIVERS
ELECTRICAL &ELECTRONICEQUIPMENT
RADIATEDCABLE-CABLECABLE-CASECASE-CABLECASE-CASE
CONDUCTEDPOWER LINESSIGNAL LINES
GROUND
ELECTRONICEQUIPMENT
EMI SOURCE(EMITTER)
PRIMARY COUPLINGMECHANISM
EMI VICTIM(RECEPTOR)
RADIATEDANT-ANT
RECEIVERS
TRANSMITTERSRADIATED
ANT-CABLEANT-CASE
ELECTRONICEQUIPMENT
RADIATEDCABLE-ANTCASE-ANT
RECEIVERS
ELECTRICAL &ELECTRONICEQUIPMENT
RADIATEDCABLE-CABLECABLE-CASECASE-CABLECASE-CASE
CONDUCTEDPOWER LINESSIGNAL LINES
GROUND
ELECTRONICEQUIPMENT
EXAMPLES OF ELECTRONIC-SYSTEM EMI
1. POWER CABLE EMISSIONS
2. POWER CABLE CONDUCTED SUSCEPTIBILITY
3. INTERCONNECTING CABLE CONDUCTED EMISSION
4. INTERCONNECTING CABLE SUSCEPTIBILITY
5. ANTENNA LEAD CONDUCTED EMISSION
6. ANTENNA LEAD CONDUCTED SUSCEPTIBILITY
EXAMPLES OF ELECTRONIC-SYSTEM EMI
7. COMMON GROUND IMPEDANCE EMISSION COUPLING
8. COMMON GROUND IMPEDANCE SUSCEPT. COUPLING
9. H-FIELD RADIATION
10. E-FIELD RADIATION
11. H-FIELD SUSCEPTIBILITY
12. E-FIELD SUSCEPTIBILITY
EMC ANALYSIS
Coupling
H();H(F)
InterferingTransmitter
SusceptibleReceiver
X(t)X(f)
y(t)Y(f)
Y(f) = H(f) Y(f)
LINEAR SYSTEMS
dτ τ)(tx )(τ h y(t)-
INTRODUCTION TO EMC DAY 1
Definition of Terms and Units
BASIC TERMS--POWER AND DB SCALE
2
110
122
1 10
1
2 10
2
1 10
1
210
22
11 10
2
110
VV log 20
ZZ when , ²
VVlog10
ZZ log10
²VVlog10
ZZ
²V2V1 log10
²/ZV²/ZVlog10
PPlog10dB
dB Power Voltage Ratio Ratio
dB Power Voltage Ratio Ratio
0 1.00 1.003 2.00 1.416 4.00 2.009 8.00 2.82
10 10 3.16 20 100 10 -10 .1 .300 -20 .01 .10
CIRCUIT AND FIELD RELATIONS
ELECTROMAGNETIC FIELDS
Time Varying Spatial Varying Electric Field Magnetic Field Velocity of Propagation Wavelength = C/ƒ (m) = 300
fMHz (ft) = 984
fMHz
ANTENNA FACTOR: RELATION BETWEEN ARRIVING FIELD STRENGTH, E, AND RECEIVER INDUCED VOLTAGE,
V.
INTRODUCTION TO EMC DAY 1
Types of EMI
NARROWBAND AND BROADBAND EMISSIONS
RECEIVER IMPULSE BANDWIDTH
t
ffc
BiVi/MHz
V=Vi/MHz • BiMHz
BiMHz= V 7dB C.W.B.W.Vi/MHz
BROADBAND EMI RELATIONSHIPS
V/MHz = V voltsBi (MHz)
20log V/MHz = 20log Volts- 20log Bi MHzdBV/MHz = dBV - BidB/MHz
EXAMPLES OF NARROWBAND EMI UNITS
Conducted
Radiated
PowerW
dBWdBm
VoltageV
dBVdBV
CurrentA
dBAdBA
Power DensityW/m2
dBW/m2
dBm/m2
Field StrengthV/m
dBv/mdBV/m
Magnetic Field (H)A/m
dBA/mdBA/m
Magnetic Flux Density (B)Tesla (Weber/m2)
Picotesla (pT)dBpT
EXAMPLES OF BROADBAND EMI UNITS
Conducted
Radiated
PowerdBm/kHz
VoltagedBV/MHz
CurrentdBA/MHz
Power DensitydBm/m2/kHz
Field StrengthdBV/m/MHz
Magnetic Field (H)dBA/m/MHz
Magnetic Flux Density (B)dBpT/MHz
FOURIER ANALYSIS
TIME DOMAIN(OSCILLOSCOPE VIEW)
Frequency Domain(Spectrum Analyzer,EMI Receiver View)
F
F0 = 1T
Sine Wave
TIME DOMAIN(OSCILLOSCOPE VIEW)
Frequency Domain(Spectrum Analyzer,EMI Receiver View)
TIME-FREQUENCY TRANSFORMATION OF PERIODIC FUNCTION
TIME-FREQUENCY TRANSFORMATION OF SINGLE PULSE
LIGHTNING, EMP, AND ELECTROSTATIC DISCHARGE
EMI IMPACT VISIBLE IN FREQUENCY DOMAIN
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