Download - Measurements using a GTEM cell above 1GHz
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Measurements using a GTEM cell above 1GHz
Dr Tian Hong LOH
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
![Page 4: Measurements using a GTEM cell above 1GHz](https://reader036.vdocuments.mx/reader036/viewer/2022062301/56815077550346895dbe755f/html5/thumbnails/4.jpg)
Introduction: What’s GTEM?
• GTEM cell – Giga-Hertz Transverse Electromagnetic cell.• Tapered Coaxial Transmission Line with 50 termination
at both ends.
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Introduction: What’s GTEM?
• Designed for use as EMC radiated emission and radiated immunity test facility without impact of the ambient electromagnetic environment.
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Introduction: What’s GTEM?
• At the input, a normal 50 coaxial line is physically transformed to a rectangular cross section.
• The cross sectional dimensions are a ratio of 3:2 horizontal to vertical cross sectional dimensions.
a
b
b/a = 3/2
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Introduction: What’s GTEM?
• The centre conductor – septum, is a flat and wide conductor that will produce a uniform electrical field distribution underneath it which form a test volume for testing the EUT.
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
![Page 9: Measurements using a GTEM cell above 1GHz](https://reader036.vdocuments.mx/reader036/viewer/2022062301/56815077550346895dbe755f/html5/thumbnails/9.jpg)
Reason for GTEM measurement above 1GHz
• The use of GTEM cell above 1GHz is still novel to product manufacturers.
• Increasing clock speed of computer processors.
• The need to measure the wave structure and to understand potential limitations in the use of the cell at higher frequencies.
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
![Page 11: Measurements using a GTEM cell above 1GHz](https://reader036.vdocuments.mx/reader036/viewer/2022062301/56815077550346895dbe755f/html5/thumbnails/11.jpg)
Equipment under test (EUT)
• Dummy device that is commissioned resembling typical products.
• Consists of monocone antenna as radiating source mounted on the inside of a metal box.
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Equipment under test (EUT)
• Power by a battery operated York EMC Services CGE01 comb generator with 100MHz harmonic spacing.
• Fundamental signal of 100MHz.• Measurable E-field from EUT up to 15GHz.
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Equipment under test (EUT)
• Small EUT (SEUT): [ (L:W:H) = 23cm 20cm 11cm ]
Side 5
Side 2Side 1
Side 5
Side 3 Side 2
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Equipment under test (EUT)
• Large EUT with complicated slots (LEUTC):
[ (L:W:H) = 12.5cm 48.5cm 48.5cm ]
Side 1
Side 2
Side 3
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
![Page 16: Measurements using a GTEM cell above 1GHz](https://reader036.vdocuments.mx/reader036/viewer/2022062301/56815077550346895dbe755f/html5/thumbnails/16.jpg)
Experimental Setup
• Instrumentation used:
1. Spectrum Analyser (PSA)
2. Microwave Amplifier
3. Cables
4. Computer System
5. GTEM cell
6. Foam Table
7. EUT
12
3
4
5
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Experimental Setup
Ver
tica
l P
olar
isat
ion
75
• Instrumentation used:
1. Spectrum Analyser (PSA)
2. Microwave Amplifier
3. Cables
4. Computer System
5. GTEM cell
6. Foam Table
7. EUT 6
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Experimental Setup
• SEUT:
1750mm1620mm
450mm535mm590mm
645mm
1
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Experimental Setup
• SEUT:
1750mm1620mm
450mm535mm590mm
645mm
1120mm
3mm483mm
538mm
12
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Experimental Setup
• SEUT:
1750mm1620mm
450mm535mm590mm
645mm
1120mm
3mm483mm
538mm
820mm
255mm
60mm370mm
425mm
12
3
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Experimental Setup
• LEUTC:
1750mm
1620mm
450mm
85mm
485mm
535mm
777.5mm
125mm
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Overview of the Presentation
• Introduction to GTEM cell
• Reason for GTEM measurement above 1GHz
• Equipment under test (EUT)
• Experimental Setup
• Experimental Results
![Page 23: Measurements using a GTEM cell above 1GHz](https://reader036.vdocuments.mx/reader036/viewer/2022062301/56815077550346895dbe755f/html5/thumbnails/23.jpg)
Experimental Results
• SEUT: Sensitivity --- Transverse displacement
0 1 2 3 4 5 6 7 8
x 109
-100
-90
-80
-70
-60
-50
-40
-30
Frequency (Hz)
Pe
ak
sea
rch
on
ha
rmo
nic
s (d
Bm
)
Emission Sensitivity Measurement - Transverse displacement (Side1 face apex)
centreL.H.S. 50mmL.H.S. 100mmR.H.S. 50mmR.H.S. 100mm
0 1 2 3 4 5 6 7 8
x 109
0
2
4
6
8
10
12
14
Frequency (Hz)
Co
mp
ari
son
(d
B)
Emission Sensitivity Measurement - Transverse displacement (Side1 face apex)
abs[ (L.H.S. 50mm) - (centre) ]abs[ (L.H.S. 100mm) - (centre) ]abs[ (R.H.S. 50mm) - (centre) ]abs[ (R.H.S. 100mm) - (centre) ]
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Experimental Results
• SEUT: Sensitivity --- Vertical displacement
0 1 2 3 4 5 6 7 8
x 109
-100
-90
-80
-70
-60
-50
-40
-30
Frequency (Hz)
Pe
ak
sea
rch
on
ha
rmo
nic
s (d
Bm
)
Emission Sensitivity Measurement - Vertical displacement (Side1 face apex)
0 1 2 3 4 5 6 7 8
x 109
0
5
10
15
20
Frequency (Hz)
Co
mp
ari
son
(d
B)
Emission Sensitivity Measurement - Vertical displacement (Side1 face apex)
620mm720mm820mm
abs[ (720mm) - (620mm) ]abs[ (820mm) - (620mm) ]
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Experimental Results
• SEUT: E-field comparison between GTEM & FAR
1 2 3 4 5 6 7 8
x 109
65
70
75
80
85
90
95
Frequency (Hz)
E f
ield
Str
en
gth
[d
B(u
V/m
)]
Comparison between Emission measurement of SEUT in GTEM and FAR
GTEM 2m E-field at 1620mm septem heightGTEM 2m E-field at 1120mm septem heightGTEM 2m E-field at 820mm septem heightFAR 2m E-field, Ant. VP, 2m away from SEUT
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Experimental Results
• LEUTC: E-field comparison between GTEM & FAR
2 4 6 8 10 12 14
x 109
40
45
50
55
60
65
70
75
80
85
90
95
Frequency (Hz)
E f
ield
Str
en
gth
[d
B(u
V/m
)]Comparison between Emission measurement of Vertically Polarised LEUTC in GTEM and FAR
GTEM, NORMAL detectorFAR, PEAK detector, Antenna Vertically Polarised, 3m away from LEUTC for all antenna heights
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Modified Experimental Setup
• LEUTC:
1750mm
1620mm
450mm85mm
485mm
535mm
777.5mm
125mm
Stepper Motor
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Experimental results
• LEUTC: E-field comparison between GTEM & FAR
2 4 6 8 10 12 14
x 109
40
45
50
55
60
65
70
75
80
85
90
95
Frequency (Hz)
E f
ield
Str
en
gth
[d
B(u
V/m
)]Comparison between Emission measurement of Vertically Polarised LEUTC in GTEM and FAR
GTEM, MAX E-field in azimuth cutGTEM, E-field obtained from three position RSS algorithmFAR, MAX E-field, VP Ant., 3m away from LEUT for all antenna heights
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Experimental results: Radiation Pattern
• Radiation pattern of LEUTC in GTEM:
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Thank you for your attention.
Any Questions?