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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

ELECTROMAGNETIC ENVIRONMENT EFFECTS (E3)

Performance degradation of receiver signal processing circuitsErroneous 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

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

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 NARROWBAND EMI UNITS

Conducted

Radiated

PowerW

dBWdBm

VoltageV

dBVdBμV

CurrentA

dBAdBμA

Power DensityW/m2

dBW/m2

dBm/m2

Field StrengthV/m

dBv/mdBμV/m

Magnetic Field (H)A/m

dBA/mdBμA/m

Magnetic Flux Density (B)Tesla (Weber/m2)

Picotesla (pT)dBpT

EXAMPLES OF BROADBAND EMI UNITS

Conducted

Radiated

PowerdBm/kHz

VoltagedBμV/MHz

CurrentdBμA/MHz

Power DensitydBm/m2/kHz

Field StrengthdBμV/m/MHz

Magnetic Field (H)dBμA/m/MHz

Magnetic Flux Density (B)dBpT/MHz

F1

Vin

TinT1

V1

V1 = F1TinVin

T1 = 1/F1

Vin

Tin

Filter Affects on a Pulse

Electric-Field Strength vs. Transmitter Distance and ERP*

Walkie Talkie Crashes Equipment

EMI MITIGATION FOR OTHER SYSTEMS

Radiated EMI Mitigation• Shielding• Circuit Design• Cable Selection and LayoutConducted EMI Mitagation• Grounding• Filters, Ferrites, Isolation Transformers, Optical

Isolators, etc.

TWO-BOX EMI SEVERAL MILLION COMBINATIONS!MANY WITH AN INFINITE RANGE OF VARIABLES.

MANIFESTATIONS

PCB

Mother Board

Multiple Sites

Site

System

Subsystem

Equipment

Component

• Battle Force - EME

• Aircraft, Ship or Building

• Fire-Control Radar, Control System

• Equipment Racks, Consoles

• R.F. Receiver, Medical Instrument

• Main Distribution to PCB

• Cards to Hold DIPS Components

• DIPS, CHIPS, Relays

COUPLING

Conducted power or signal cable coupling

Common-ground impedance common-mode coupling

Field-to-Cable or Cable-to-Field common-mode coupling

Field-to-cable or Cable-to-Field differential-mode coupling

Cable-to-Cable differential-mode coupling

Case Radiation-Case Penetration

CONDUCTED EMI

“EMI always start out at the culprit andends up at the victim as a conducted

signal regardless of what goes on between these two points!”

Power Source Load

Figure 4. Illustration of Common Mode Currents

CMC 1

CMC 2

CMC

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Metallic Structure

Illustration of Common Mode Currents

Power Source Load

DCM1

DCM2

Figure 3. Illustration of Differential Mode Currents

Illustration of Differential Mode Currents

Power Source LoadCMC 1

CMC 2

CMC

Metallic Structure

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Figure 5. Illustration of Common and Differential Mode Currents

DMC 1

DMC 2

Illustration of Common and Differential Mode CurrentsIllustration of Common and Differential Mode Currents

Illustration of Common and Differential Mode Currents

Power Source LoadCMC 21

CMC 21

CMC1

Metallic Structure

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Figure 6. Common Mode Currents Resulting From Distributed Capacitance to Ground

Common Mode Currents Resulting FromDistributed Capacitance to Ground

Power Source LoadCMC

CMC

EMI'

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Metallic Structure

Figure 10. Common Ground Impedence Common Mode EMI

EMI

Common Ground Impedance Common Mode EMI

Controlling Conducted EMI

Source

Power SuppliesMotors

Inductive LoadsHigh Level Analog

Digital SignalsTransmitters

EM Environment

Victim

Analog EquipmentDigital Equipment

Video DisplayRecorders

InstrumentsSensors

Control SystemsReceivers

Conducted EMI

Applicable EMI Control Techniques

PowerFilterFerritesIsolation TransformersTranslent Suppressors

SignalFiltersFerritesIsolation TransformersTranslent Suppressors

PowerFiltersFerritesIsolation TransformersBalanced SystemsFloatInductor in Ground

SignalFilterFerriteIsolation TransformersBalanced CircuitFloatInductor in GroundOptical Isolator

Differential Mode Common Mode (Ground Loop)

WHAT IS GROUND ?

• SIGNAL RETURN?

• CHASSIS REFERENCE?

• SAFETY WIRE REFERENCE?

• EARTH REFERENCE?

GROUNDING HIERARCHY

GROUNDING CONDUCTOR IMPEDANCE VS. FREQUENCY

Using Ferrites to Absorb Common-Mode EMI

PRINCIPAL RADIATION SOURCES ON PRINTED CIRCUIT BOARD

Logic familiesclock rates

• Large single-layer board• PCB card cage with back plane• Multi-layer board

Radiation from ribbon cables

Radiation from IC dips

MAGNETIC FIELDS FROM A TWISTED PAIR OF CONDUCTORS (TRANSPOSITION)

I2

I2I1

I1

ΔV2 ΔV1

Area 1Area 2

V RL

REPRESENTATION OF SHIELDING PHENOMENAREPRESENTATION OF SHIELDING PHENOMENAFOR PLANE WAVESFOR PLANE WAVES

Outside World

Inside of Enclosure

Incident Wave

AttenuatedIncident

Wave

A

Ey

HzEy

Ey

EyHz Hz

Hz

H

Internal ReflectingWaveMetal

Barrier

ReflectedWave

Transmitted WaveB

Ey

PRINCIPAL BOX SHIELDING COMPROMISESPRINCIPAL BOX SHIELDING COMPROMISES

Connectors

Fuse

Switch

PotentiometerPanel Meter

StatusIndicator

Lamp

Cover Platefor Access

Holes or Slotsfor Convection Cooling

Screw Spacing= Slot Radiation

Forced AirCooling

Some System EMC Fix Applications

PP47645A

PP47645A