Bicsi3

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CORRELATION BETWEEN RADIATED IMMUNITY AND
COUPLING ATTENUATION Michiel Pelt
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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

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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

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Introduction

• A near field measurement

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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

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Coupling attenuation

• Coupling attenuation

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Coupling attenuation

• Definition coupling attenuation

ac 10 LOG10 ( P1 )
max P2n P2f
ac coupling attenuation P1 input power inner
circuit P2n maximum near end peak
power P2f maximum far end peak power
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Coupling attenuation

• Limits of coupling attenuation

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Coupling attenuation

• Unshielded twisted pair cable

54 dB
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Coupling attenuation

• Coaxial cable

52 dB
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Coupling attenuation

• Dual foil twisted pair cable

86 dB
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Radiated immunity

• Radiated immunity
• Semi-anechoic room (13.2 x 4.7 x 3.0m)
• Antenna - set-up 3 m
• Three amplifiers, two antennas
• 30 - 200 MHz
• 200 - 500 MHz
• 500 - 1000 MHz
• Incident field about 3 V/m (not modulated)

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Radiated immunity

• Dimensions cabling set-up

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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)

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Radiated immunity

• Set-up inside semi-anechoic chamber

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Radiated immunity

• Set-up inside semi-anechoic chamber

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Radiated immunity

• Uniform area of cabling set-up

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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)

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Radiated immunity

• Average field strength

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Radiated immunity

• Unshielded twisted pair cable

-35 dBm
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Radiated immunity

• Coaxial cable

-35 dBm
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Radiated immunity

• Dual foil twisted pair cable

-70 dBm
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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

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Correlation

• Gain of set-up

G(????) 4 ??Af(????) ??
G(????? antenna gain Af(????? antenna
aperture ? wavelength
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Correlation

• Unshielded twisted pair cable

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Correlation

• Coaxial cable

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Correlation

• Dual foil twisted pair cable

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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

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Conclusions

• Errors during correlation
• Incident field uniform but not constant
• Gain set-up varies with frequency
• Coupling attenuation approached by envelope curve
• ...