Efficient and accurate measurement of the radiated emission at high frequencies can be a challenge, especially for electrically large unintentional radiators and devices under test. This talk will explain the procedure as well as the corresponding advantages and disadvantages for different EMC test environments such as anechoic rooms, wave guides, and reverberation chambers.
Introduction to IEEE STANDARDS and its different types.pptx
Robust, Precise, Fast - Chose Two for Radiated EMC Measurements!
1. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Robust, Precise, Fast
Chose Two for Radiated EMC Measurements!
Dr.-Ing. Mathias Magdowski
Chair for Electromagnetic Compatibility
Institute for Medical Engineering
Otto von Guericke University Magdeburg, Germany
February 27, 2024
License: cb CC BY 4.0 (Attribution, ShareAlike)
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3. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Motivation
Ensuring electromagnetic compatibility:
▶ Will there be a radiated disturbance or interference?
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4. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Don’t be that kind of test engineer!
Source: https://imgflip.com/i/8h538q
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5. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Fundamental questions
What is a good measurand for emission?
▶ field strength in V
m (in a certain distance)
▶ power flux density in W
m2 (in a certain distance)
▶ total radiated power W (independent of the distance)
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6. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Fundamental questions
What is a good measurand for emission?
▶ field strength in V
m (in a certain distance)
▶ power flux density in W
m2 (in a certain distance)
▶ total radiated power W (independent of the distance)
In which environment is the measurement performed?
▶ reflection-free environment
▶ environment with reflections
▶ highly reflective environment
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7. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Overview
Measurements in semi-anechoic chambers
Measurements in reverberation chambers
Conversion of results
Emission measurements with a generic EUT
Summary
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 5 / 40
8. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Simple idea of a semi-anechoic chamber
Figure: Schematic measurement setup in a semi-anechoic chamber (top view)
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9. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Practical semi-anechoic chamber
Figure: Semi-anechoic chamber with 10 m measurement distance in Magdeburg
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10. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Measurand
What you would like to measure:
▶ radiated field strength in the far field
▶ maximum over all directions for all frequencies
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 8 / 40
11. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Measurand
What you would like to measure:
▶ radiated field strength in the far field
▶ maximum over all directions for all frequencies
What you actually measure:
▶ radiated field strength at a certain distance
▶ maximum over each sampled direction for each measured frequency
▶ radiation upwards (and downwards) is neglected
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12. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Overview
Measurements in semi-anechoic chambers
Measurements in reverberation chambers
Conversion of results
Emission measurements with a generic EUT
Summary
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 9 / 40
13. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Simple idea of a reverberation chamber
Figure: Schematic setup of a reverberation chamber (top view)
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14. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Practical reverberation chamber
Figure: Large reverberation chamber in Magdeburg
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15. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Think about it!
Source: https://imgflip.com/i/6sa6a6
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16. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
How to stir the field?
Changes of the electromagnetic boundary conditions:
▶ mechanical stirrer(s)
▶ moving walls
▶ relocating the antenna(s)
▶ switching between several antennas
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17. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
How to stir the field?
Changes of the electromagnetic boundary conditions:
▶ mechanical stirrer(s)
▶ moving walls
▶ relocating the antenna(s)
▶ switching between several antennas
Narrow band frequency changes:
▶ only for immunity testing
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18. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Vibrating intrinsic reverberation chamber
(a) Demonstration with neon tubes (b) In-situ test on a ship
Source: Prof. Leferink, University of Twente and THALES, Netherlands
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19. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Oscillating wall stirrer
Figure: Reverberation chamber with an oscillating wall stirrer at the Laboratory of
Electromagnetic Compatibility, School of Mechanical Engineering, Southeast University,
Nanjing, China
Source: https://dx.doi.org/10.1109/TEMC.2020.2983981
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20. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Statistical properties of the field
Homogeneity:
▶ uniformity over the space
▶ free placement of the EUT in the working volume
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21. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Statistical properties of the field
Homogeneity:
▶ uniformity over the space
▶ free placement of the EUT in the working volume
Isotropy:
▶ uniformity in all directions
▶ orientation of the EUT does not matter
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22. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Statistical properties of the field
Homogeneity:
▶ uniformity over the space
▶ free placement of the EUT in the working volume
Isotropy:
▶ uniformity in all directions
▶ orientation of the EUT does not matter
Validity:
▶ only in the working volume
▶ minimum distance to the walls > λ
4
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23. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Change my mind!
Source: https://imgflip.com/i/6sa4e8
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24. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Measurand
What you would like to measure:
▶ total radiated power for all frequencies
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25. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Measurand
What you would like to measure:
▶ total radiated power for all frequencies
What you actually measure:
▶ total radiated power for each measured frequency
▶ but falsified by the statistical uncertainty of the measurement
▶ Background: remaining field inhomogeneity, limited sample size
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26. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Measurand
What you would like to measure:
▶ total radiated power for all frequencies
What you actually measure:
▶ total radiated power for each measured frequency
▶ but falsified by the statistical uncertainty of the measurement
▶ Background: remaining field inhomogeneity, limited sample size
For what limits exist:
▶ maximum radiated field strength at a certain distance
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27. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Overview
Measurements in semi-anechoic chambers
Measurements in reverberation chambers
Conversion of results
Emission measurements with a generic EUT
Summary
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28. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical size of an equipment under test
a
Definition as k · a:
k: wave number, k = 2πf
c = 2π
λ
a: radius of the smallest sphere surrounding the
EUT
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29. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical size of an equipment under test
a
Definition as k · a:
k: wave number, k = 2πf
c = 2π
λ
a: radius of the smallest sphere surrounding the
EUT
Questions:
▶ What belongs to the EUT (case, cables, . . . )?
▶ Which cable length has to be considered?
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30. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical small EUTs
Condition: k · a ≤ 1
Figure: Radiation pattern of a small dipole (Source: Wikipedia)
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31. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical large EUTs
Condition: k · a > 1
Figure: Radiation pattern (planar cut) of a practical EUT (Source: Magnus Höijer, FOI)
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32. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical large EUTs
Condition: k · a > 1
Figure: Radiation pattern (planar cut) of a practical EUT (Source: Magnus Höijer, FOI)
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 22 / 40
33. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Electrical large EUTs
Condition: k · a > 1
Figure: Radiation pattern (planar cut) of a practical EUT (Source: Magnus Höijer, FOI)
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 22 / 40
34. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
The higher the frequency, the larger the problem!
Source: https://imgflip.com/i/6sagu4
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35. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Directivity
Definition:
D(ϑ, φ) =
Φ(ϑ, φ)
Prad/4π
(1)
▶ Φ is the power density radiated per solid angle
▶ Prad is the total radiated power
▶ Prad/4π is the average radiated power
Maximum directivity Dmax:
▶ Directivity in the main beam direction
▶ electrically short dipole: Dmax = 3/2 = 1.76 dBi
▶ electrically large EUT: Dmax ≈ 10 = 10 dBi
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36. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Free space or fully anechoic room (FAR)
Relationship between power and field strength:
E2
max = Dmax
η0
4πr2
Prad (2)
▶ η0 is the free space impedance
▶ r is the distance
▶ derivation with the help of a short electric dipole
▶ valid in the far field
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37. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Half space or semi-anechoic chamber (SAC)
Relationship between power and field strength:
E2
max = Dmax
η0
4πr2
Prad g2
max (3)
▶ gmax is an additional geometry factor
▶ value range between 0 and 2
▶ consideration of the reflection at the ground plane
▶ interference of the direct and the reflected wave
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39. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Conversion SAC to RC w. r. t. f for a = 0.75 m and r = 10 m
107
108
109
1010
0
2
4
6
8
10
12
14
Frequency, f in Hz
Conversion
factor
E
2
max
P
rad
in
V
2
W
m
2
95. percentile
average
50. percentile
5. percentile
https://octav.onl/corr_OATS_RC
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40. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Conversion FAR to RC w. r. t. f for a = 0.75 m and r = 3 m
107
108
109
1010
0
5
10
15
20
25
Frequency, f in Hz
Conversion
factor
E
2
max
P
rad
in
V
2
W
m
2
95. percentile
average
50. percentile
5. percentile
https://octav.onl/corr_FAR_RC_f
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41. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Conversion between FAR and RC with respect to ka for r = 10 m
10−1
100
101
102
103
0
0.5
1
1.5
2
2.5
3
Product of wavenumber and EUT size, ka
Conversion
factor
E
2
max
P
rad
in
V
2
W
m
2
95. percentile
average
50. percentile
5. percentile
https://octav.onl/corr_FAR_RC
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42. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 31 / 40
43. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Environment: deterministic
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44. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Environment: deterministic
EUT: random
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 31 / 40
45. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Environment: deterministic
EUT: random
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 31 / 40
46. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Environment: deterministic
EUT: random
Environment: random
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 31 / 40
47. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Which type of measurement would you like to have?
Environment: deterministic
EUT: random
Environment: random
EUT: deterministic
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 31 / 40
48. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Overview
Measurements in semi-anechoic chambers
Measurements in reverberation chambers
Conversion of results
Emission measurements with a generic EUT
Summary
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 32 / 40
49. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Emission measurements with a generic EUT
(a) in the reverberation chamber (b) in the semi-anechoic chamber
Figure: Utilized equipment under test (Source: Matthias Hirte, OVGU)
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50. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Emission measurements with a generic EUT
200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1 000
55
60
65
70
75
Frequency in MHz
Field
strength
in
dB
µV
m Measurement in the semi-anechoic chamber
Measurement in the reverberation chamber
Figure: Comparison of the emission measurement in different environments, directivity = 1
(Source: Matthias Hirte, OVGU)
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51. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Emission measurements with a generic EUT
200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1 000
55
60
65
70
75
Frequency in MHz
Field
strength
in
dB
µV
m 10◦ steps
90◦ steps
Figure: Comparison of the emission measurement for different turntable steps (Source:
Matthias Hirte, OVGU)
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52. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Overview
Measurements in semi-anechoic chambers
Measurements in reverberation chambers
Conversion of results
Emission measurements with a generic EUT
Summary
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 36 / 40
53. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Catch my radiation, if you can!
Source: https://imgflip.com/i/6sae2q
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 37 / 40
54. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
There is a solution, wait, not.
Source: https://imgflip.com/i/6sahm3
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 38 / 40
55. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
All good things are never together.
robust
precise fast
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 39 / 40
56. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
All good things are never together.
robust
precise fast
reverberation
chamber
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 39 / 40
57. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
All good things are never together.
robust
precise fast
reverberation
chamber
semi-anechoic
chamber
(full sampling)
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 39 / 40
58. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
All good things are never together.
robust
precise fast
reverberation
chamber
semi-anechoic
chamber
(full sampling)
semi-anechoic chamber
(undersampling for known radiators)
Mathias Magdowski Robust, Precise, Fast – Chose Two! 2024-02-27 39 / 40
59. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
All good things are never together.
robust
precise fast
reverberation
chamber
semi-anechoic
chamber
(full sampling)
semi-anechoic chamber
(undersampling for known radiators)
perfect
test
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60. Semi-anechoic chambers Reverberation chambers Conversion of results Generic EUT Summary
Source: https://twitter.com/MarkusRidderbu8/status/
1523708966039351297
Thank you very much for
your attention!
Are there any questions?
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