CORRELATION BETWEEN RADIATED IMMUNITY AND COUPLING ATTENUATION Michiel Pelt

Michiel Pelt, Nexans Cabling Solutions, Alsembergsestw 2b3, B-1501 Buizingen, Belgium

CORRELATION BETWEEN

RADIATED IMMUNITY

AND

COUPLING ATTENUATION

Michiel Pelt


Introduction

Need for new test method:

No test methods to measure: symmetrical cables, connecting

hardware / cable assemblies balance at higher frequencies combined effect of balance and

screening


Introduction

Coupling attenuation

New and easy test method to evaluate the EMC performance of channels and components (symmetrical + screened)

Standard prepared by CENELEC TC 46X / WG3: EN 50289-1-6

Under discussion in ISO / IEC JTC1 SC25 WG 3 and CLC TC 215 WG 1


Introduction

A near field measurement


Introduction

Simplifications

Device under test: unshielded twisted pair cable coaxial cable dual foil balanced cable

Radiated immunity according to IEC 61000-4-3 fixed position antenna and device



Definition coupling attenuation

ac = 10 LOG10 ( P1 ) max [ P2n; P2f ]

ac coupling attenuationP1 input power inner circuitP2n maximum near end peak powerP2f maximum far end peak power



Limits of coupling attenuation



Unshielded twisted pair cable

0

30

60

90

120

10 100 1000

FREQUENCY (in MHz)

CO

UP

LIN

G A

TT

EN

UA

TIO

N(i

n d

B)

54 dB



Coaxial cable

0

30

60

90

120

10 100 1000

FREQUENCY (in MHz)

CO

UP

LIN

G A

TT

EN

UA

TIO

N(i

n d

B)

52 dB



Dual foil twisted pair cable

0

30

60

90

120

10 100 1000

FREQUENCY (in MHz)

CO

UP

LIN

G A

TT

EN

UA

TIO

N(i

n d

B)

86 dB


Radiated immunity

Radiated immunity

Semi-anechoic room (13.2 x 4.7 x 3.0m)Antenna - set-up: 3 mThree amplifiers, two antennas

30 - 200 MHz 200 - 500 MHz 500 - 1000 MHz

Incident field: about 3 V/m (not modulated)


Radiated immunity

Dimensions cabling set-up


Radiated immunity

Justification for cabling set-up

Testing active equipment with cabling (proposal to CISPR G)

Features cabling set-up: gain / frequency response flat polarization not critical direction not critical

(worst case perpendicular to incident field)


Radiated immunity

Set-up inside semi-anechoic chamber


Radiated immunity

Uniform area of cabling set-up


Radiated immunity

Field uniformity according to

IEC 61000-4-3

16 points over 1.5 m x 1.5 m surface 75 % values within 0 - 6 dB of nominal

value Field is not constant but uniform

( 83% horizontal; 89 % vertical)


Radiated immunity

Average field strength

0.0

2.5

5.0

7.5

10.0

0 200 400 600 800 1000

FREQUENCY (MHz)

FIE

LD

ST

RE

NG

TH

(V

/m)


Radiated immunity


-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)

-35 dBm


Radiated immunity

Coaxial cable

-35 dBm

-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)


Radiated immunity


-70 dBm

-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)


Conclusions

Conclusion 1: Relative agreement

Same difference between coupling attenuation and induced power for all tested cables

For each test method same deviation between curves for balanced and unbalanced cables using


Correlation

Gain of set-up

G() = 4 Af()

G( antenna gainAf( antenna aperture wavelength


Correlation


-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)


Correlation

Coaxial cable

-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)


Correlation


-100

-80

-60

-40

-20

0

0 200 400 600 800 1000

FREQUENCY (MHz)

PO

WE

R (

dB

m)


Conclusions

Conclusion 2: Absolute agreement

The induced noise power can be calculated using the values for coupling attenuation

The calculated induced power fits the measured powers for all cables


Conclusions

Errors during correlation

Incident field uniform but not constantGain set-up varies with frequencyCoupling attenuation approached by

envelope curve ...

CORRELATION BETWEEN RADIATED IMMUNITY AND COUPLING ATTENUATION Michiel Pelt

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