Electro Magnetic Compatibility

8/4/2019 Electro Magnetic Compatibility

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Aug 20, 2011Aug 20, 2011 ir. W.J. Vogel - www.mate.nl .ir. W.J. Vogel - www.mate.nl . 11

Electro MagneticElectro Magnetic

Compatibility.Compatibility.

A new approach for findingA new approach for finding

solutions for interferencesolutions for interferenceproblems.problems.

Ir. W.J. Vogel Ir. W.J. Vogel www.mate.nlwww.mate.nl
http://./http://./http://./


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Fundamentals of EMC: Units and Symbols.Fundamentals of EMC: Units and Symbols.

Duality between Electricity andDuality between Electricity and

Magnetism.Magnetism.

Electric field strength E V/m or N/CElectric field strength E V/m or N/C

Electric charge Q C or AsElectric charge Q C or As

Electric Voltage U V or J/CElectric Voltage U V or J/C

Capacitance C F or C/VCapacitance C F or C/V

Electr. Charge density D C/mElectr. Charge density D C/m22

Electr. PermittivityElectr. Permittivity F/mF/m

U = - dU = - d/dt V or Wb/s/dt V or Wb/s

Energy density = D.E J/mEnergy density = D.E J/m33

Vacuum PermittivityVacuum Permittivity 00= 8.85 pF/m= 8.85 pF/m

Light velocity (vacuum) cLight velocity (vacuum) c00

= 3.10= 3.1088 m/sm/s

cc0022= (= (00 00))

-1-1

Wave impedance in free space:Wave impedance in free space:

Zo = (Zo = (0/0/ // 00))0.50.5 = 120= 120 (())

Magnetic field strength H A/m orMagnetic field strength H A/m or

N/WbN/Wb

Magnetic fluxMagnetic flux Wb or VsWb or Vs

Electric current I A or J/WbElectric current I A or J/Wb

Inductance L H orInductance L H orWb/AWb/A

Magn. Flux density B Wb/mMagn. Flux density B Wb/m22

Magn. PermeabilityMagn. Permeability H/mH/m

Current density J A/Current density J A/mm22

Magnetic pole strength qMagnetic pole strength qmm

AmAm

I = dQ/dt A or C/sI = dQ/dt A or C/s

Energy density = B.H J/mEnergy density = B.H J/m33

Vacuum PermeabilityVacuum Permeability 00= 1.26= 1.26

H/mH/m


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Fundamentals of EMC:Fundamentals of EMC:

Coupling paths.Coupling paths.

Through common electric conductors.Through common electric conductors. Direct radiation from/to the outside world.Direct radiation from/to the outside world.

(E/H) = 120(E/H) = 120 ( ). ( ). [ far field, flat wave in free space ].[ far field, flat wave in free space ].

Capacitive (E-field) coupling.Capacitive (E-field) coupling.

Inductive (H-field) coupling.Inductive (H-field) coupling. Transmission line (E- + H-field) coupling.Transmission line (E- + H-field) coupling.


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Electric Field (1).Electric Field (1).

Electric field linesbetween twoconductors withequal and opposite

electric charge.


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Electric Field (2).Electric Field (2).

Electric field lines between theplates of a flat capacitor (sideeffects not considered).


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Magnetic Field (1).Magnetic Field (1).

Magneticfieldlinesaround a

straight currentcarrying wire.


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Magnetic fieldlines through around current

carrying loop.


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Magnetic fieldlines through acurrent carrying

solenoid.


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Impedance of EMImpedance of EM

fields.fields. Flat wave in free space: Impedance =Flat wave in free space: Impedance = (E/H) = 120(E/H) = 120 ( ) ( ) ( far field; r >>( far field; r >>

).).

For the near field, other rules apply !For the near field, other rules apply !

If (E/H) >> 120If (E/H) >> 120 ( ) ( ), then it is a high-, then it is a high-impedant field.impedant field. If (E/H)


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Impedance of EMImpedance of EM

fields.fields. If (E/H) >> 120If (E/H) >> 120 ( ) ( ), then it is a high-impedant field., then it is a high-impedant field.

If (E/H)


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Power andPower and

fieldstrength.fieldstrength. Flat wave in free space: Impedance =Flat wave in free space: Impedance =

(E/H) = 120(E/H) = 120 ( ). ( ).

Power per mPower per m22: S = E x H ( W/m: S = E x H ( W/m22 ).).

Surface of a sphere around an isotropeSurface of a sphere around an isotrope

antenna = 4antenna = 4 rr22

=>> E = (30 P)=>> E = (30 P)0.50.5 / r ./ r .

For a dipole antenna: E = 7 . (P)For a dipole antenna: E = 7 . (P)0.50.5 / r ./ r .


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When occursWhen occurs

interference betweeninterference between

two EM systems?.two EM systems?. When there is a source of interference.When there is a source of interference. When there is a device which isWhen there is a device which is

susceptible for interference.susceptible for interference. When there is a coupling path.When there is a coupling path.

[ SOURCE => COUPLING PATH =>[ SOURCE => COUPLING PATH =>

SUSCEPTIBLE DEVICE ]SUSCEPTIBLE DEVICE ]


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When occursWhen occurs

interference betweeninterference between

two EM systems?.two EM systems?. [ SOURCE => COUPLING PATH =>[ SOURCE => COUPLING PATH =>

SUSCEPTIBLE DEVICE ]SUSCEPTIBLE DEVICE ]

To prevent EMC problems, sufficient marginsTo prevent EMC problems, sufficient margins

have to be realized for all three subjects.have to be realized for all three subjects.

=> Margins following the law requirements.=> Margins following the law requirements. => Margins following the user requirements.=> Margins following the user requirements.


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Types of Electro MagneticTypes of Electro Magnetic

Interference between twoInterference between two

systems.systems. Degradation of performance.Degradation of performance. Missing functions of the system.Missing functions of the system.

Components becoming defect.Components becoming defect.

=> Consequences for the quality=> Consequences for the quality

and the safety of the product =>and the safety of the product =>Can lead to claims from the end-Can lead to claims from the end-user of the product.user of the product.


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Generating Interference andGenerating Interference and

being interfered..being interfered..

Sources of interference can haveSources of interference can have

a narrowband (sine) or aa narrowband (sine) or a

wideband (pulse or noise)wideband (pulse or noise)characteristic.characteristic.

Sources of interference can causeSources of interference can cause

problems inside and outside theproblems inside and outside thefrequency range of thefrequency range of the

susceptible device.susceptible device.


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Aug 20, 2011Aug 20, 2011

ir. W.J. Vogel - www.mate.nl .ir. W.J. Vogel - www.mate.nl .

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Narrowband: Mosttransmitters, Oscillators.

Wideband: Spark bridges (ignitionsystems), SMPS, Collectormotors,

Thermostats, Frequency control

systems, Power control systems,Dimmers.


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ir. W.J. Vogel - www.mate.nl .ir. W.J. Vogel - www.mate.nl .

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Inside the frequency range of theInside the frequency range of thesusceptible device: main cause is directsusceptible device: main cause is directradiation or coupling into the device.radiation or coupling into the device.

Outside the frequency range of theOutside the frequency range of thesusceptible device: main cause issusceptible device: main cause isrectification of the interfering signal (LFDrectification of the interfering signal (LFD= Low Frequency Detection).= Low Frequency Detection).

The function of a device is disturbedThe function of a device is disturbed

when the output of the device deviateswhen the output of the device deviatesmore than whats expected from the ownmore than whats expected from the ownnoise of the device.noise of the device.


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Detection ofDetection of

Interference.Interference.Equipment:

Signal generator.

E-field probe.H-field probe.Oscilloscope.Spectrumanalyzer.EMI testreceiver.


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Reciprocity.Reciprocity.

Passive probes are usable in twoPassive probes are usable in two

directions:directions:

1. For detection of signals.1. For detection of signals.

2. For inducing of signals.2. For inducing of signals.

Active probes are not reciprocal; theseActive probes are not reciprocal; these

are only usable in one direction asare only usable in one direction as

detector.detector.


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Properties of probes.Properties of probes.

Dimensions are smallcompared to thewavelength of thesignal.

E-field probe is high-impedant (short whip).

H-field probe is low-impedant (small loop).


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Kirchhoffs lawsKirchhoffs laws

Currents to a node:Currents to a node: i = 0 .i = 0 .

Voltages in a closed loop:Voltages in a closed loop: u = 0 .u = 0 .

Real:Real: u = - du = - d / dt because the loop area is not equal/ dt because the loop area is not equal

to zero!to zero!

Electric field generated by a time-varying magneticfield;(a) d/dt > 0 ; u < 0.(b) d/dt < 0 ; u > 0.


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How to find solutions forHow to find solutions for


Interference.Interference.Position the PCB in anEM field.Look for the frequenciesat which the

interference is at itsmaximum.Localize the susceptiveor the generatingdevices by using H-fielden E-field (inductive and

capacitive) probes.

Example: locating a whistle problem in a radioreceiver.


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Interference.Interference.Try to minimize the problem byusing decoupling capacitors anddamping resistors or ferrite beads.

Investigate the signal paths andthe return paths.

Example: The effect of resonancein a series tuned circuit.


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Interference.Interference. Parallel connection of capacitors: NOTParallel connection of capacitors: NOT

ALWAYS OK!ALWAYS OK!

Cause: Self-inductance of the conductorsCause: Self-inductance of the conductors

(PCB tracks) between the capacitors.(PCB tracks) between the capacitors.

Better solution: Connect impedances (ferriteBetter solution: Connect impedances (ferrite

beads) in the power line when the signalsbeads) in the power line when the signals

have been referred to ground (GND).have been referred to ground (GND).


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Interference.Interference. Try to minimize the problemby using a better DCoperating point for thesemiconductors in thecircuit.

Investigate theconsequences for batteryconsumption, noiseproperties, bandwidth, etc.

Diode characteristics(1N4148).


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Practical Examples (1).Practical Examples (1).

Sensor for outdoor lightingsystem causes interferencein Mediumwave radioreceivers.

Root cause: Wrongapplication of the product.

Solution: Use the sensor incombination with a

conventional light bulb oruse another sensor type incombination with an energy-saving lighting system.


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Solving a whistle problem at MW in a radioreceiver by using 4 extra components at thePCB.


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In a repaired TV set theteletext function ismissing.

Root cause: Other H-fieldpattern due to anotherHorizontal OutputTransformer type.

Solution: Mount an extra

ground wire connectionbetween the control PCBand the teletext PCB.

Above: Common ground wire.Below: One-point groundingsystem.


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PCB on which a certain ICbecomes regularly defective.

Root cause: Signal path and

return path (ground) arecovering a large area.

Solution: Mount extra groundconnections at the PCB.

Above: Improved one-point groundingsystem.Below: Multiple-point grounding system.


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Practical ExamplesPractical Examples

(5a).(5a). PCB on which the twoinductors right beloware coupling due tomounting close

together.

FM Band reject filtercharacteristics arenow dependant of thephasing of the

inductors: couplingmay become positiveor negative.

Solution: Increase thedistance between the

inductors at the PCB.


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Practical ExamplesPractical Examples

(5b).(5b). Influence of the phasingof the inductors:

Red: Coupling = + 5%Blue: Coupling = - 5%

Frequency/ Hertz

100k 200k 400k 1M 2M 4M 10M 20M 40M 100M 400M 1G

?

-80

-70

-60

-50

-40

-30

-20

-10

0


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Whats the trend (1)?Whats the trend (1)?

Frequency range of EMC is increasing !Frequency range of EMC is increasing !

Examples:Examples:

GSM (cell) phones (900 MHz => 1800GSM (cell) phones (900 MHz => 1800

MHz).MHz).

Magnetrons (2450 MHz).Magnetrons (2450 MHz).

=> Extra investments are necessary for=> Extra investments are necessary for

good EMC measurement set-ups.good EMC measurement set-ups.


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The current consumption ofThe current consumption of

semiconductors is decreasing; thesemiconductors is decreasing; the

number of semiconductors in anumber of semiconductors in acircuit is increasing !circuit is increasing !

=> The susceptibility for RF sources=> The susceptibility for RF sourcesis becoming more worse !is becoming more worse !


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The dimensions of the circuits areThe dimensions of the circuits are

becoming smaller due tobecoming smaller due to

miniaturization, SMD technologyminiaturization, SMD technologyand integration !and integration !

=> The susceptibility for RF sources=> The susceptibility for RF sourcesis shifting to higher frequencies !is shifting to higher frequencies !


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The switching times ofThe switching times ofsemiconductors are becomingsemiconductors are becomingshorter !shorter !

Example: SMPS.Example: SMPS.

=> The interfering sources will=> The interfering sources willproduce more power at higherproduce more power at higherfrequencies !frequencies !


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Conclusion:Conclusion:

Recognizing EMC problems andRecognizing EMC problems andfinding solutions is more actualfinding solutions is more actual

than it ever was before !than it ever was before !

A good EMC product design fromA good EMC product design fromthe begin of the productthe begin of the product

development will save additionaldevelopment will save additionalcosts through the whole productcosts through the whole productlife cycle !life cycle !


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Contact information:Contact information:

Website:Website: www.mate.nlwww.mate.nl ..

Ir. W.J. Vogel - consultancyIr. W.J. Vogel - consultancy

E-mail:E-mail: [email protected]@gmail.com

Kramersstraat 2, 5612 NV EindhovenKramersstraat 2, 5612 NV Eindhoven

Tel. +31 40-7850345, GSM +31 6-29393856.Tel. +31 40-7850345, GSM +31 6-29393856.
http://./http://./mailto:[email protected]:[email protected]:[email protected]://./

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Electro Magnetic Compatibility