interface and cabling characterization for ska paul van der merwe prof. hc reader stellenbosch...
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![Page 1: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/1.jpg)
Interface and cabling characterization for SKA
Paul van der Merwe
Prof. HC Reader
Stellenbosch University
![Page 2: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/2.jpg)
Introductory background
2007• Masters program: -Fundamental EMC principles.
-RFI mitigation. -Accurate measurements.
• Cable trays Enclosures • Verify results screened room measurements
using computational analysis.2008
• PhD continuation cable tray measurements: -End-terminations and
mid-span connections.-Plane wave radiation.
• Simulation of pedestal base.
![Page 3: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/3.jpg)
Cable tray connections: Visualizing Physics
• No clear definition end-terminations and mid-span connections.
• Two models, two methods inducing CM currents.
• Investigated connections specified standards and EMC literature.
• Screened room measurement.
• Explained results current and field arguments.
Model 1 Model 2
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Cable tray connections (cont): Current analysis
Model 1 • Indirect current injection.
• Concentrated induced CM current.
• Separate excitation and victim loops.
• Mid- and end-connections major current diversion increased path impedance high coupling.
Model 2• Direct current injection.
• Uniform CM current distribution.
• Cable tray common conductor.
• Small current diversion for connections path impedance constant invariant coupling.
Model 1 Model 2
![Page 5: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/5.jpg)
Cable tray connections (cont 2): Field analysis
Model 1 • Resultant magnetic field combination primary field and secondary field.• Current flow influence strength of secondary field. • Secondary subtract primary field.• Side straps and L-brackets – high coupling. Wide bottom connection or U-bracket –
low coupling.
Model 2
• Excitation and victim loop connected via cable tray common conductor.• Interference coupling to victim loop constant regardless of connection type.• Same field intersects victim loop regardless type of end- or mid-connection.
Model 1 Model 2
![Page 6: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/6.jpg)
Cable tray connections (cont 3): Typical Results
Model 1
Model 2
0 10 20 30 40 50 60 70 80 90 100-140
-120
-100
-80
-60
-40
|S21
| in
dB
Frequency(MHz)
Magnitude of S21 coupling in dB
Bottom connectionL-bracketFull U-bracketSide straps
0 10 20 30 40 50 60 70 80 90 100-55
-50
-45
-40
-35
-30
-25
|S21
| in
dB
Frequency(MHz)
Magnitude of S21 coupling in dB
Bottom connectionCentre L-bracketSide strapsFull U-bracket
![Page 7: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/7.jpg)
Radiation of cable trays: Visualizing the problem
• Lower frequency analysis complete, next step HF radiation.
• One model used: -Anechoic chamber
-OATS
• Absorbing anechoic chamber, ground reflections OATS.
• LPDA and horn antennas used.
• Purpose: Comparison measured data with computed data using plane wave excitation.
![Page 8: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/8.jpg)
Radiation of cable trays (cont): Adaptation
Bad Luck• Initial measurement procedure using VNA.• VNA calibration.• VNA not performing satisfactorily on day of measurement.• Signal generator and SA.• Uncalibrated system cable loss added in post-processing.
Good Luck• Voltage calculated in computation - voltage available from
measurements.• Signal generator as transmitter, SA as receiver: voltage into 50 Ω
load calculated.
• Antenna input power known, compensate S11 mismatch.
![Page 9: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/9.jpg)
Radiation of cable trays (cont 2): Compensation
OATS influences
• OATS has reflective ground plane.
• Minimize ground reflection, placing receiver close to ground.
• Interference removed by calculating phase change along reflected path.
• Computation included ground plane therefore multi-path interference.
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
x 109
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Por
t vo
ltage
Frequency(Hz)
Voltage induced on pickup wire inside cable tray using measured and computed data
Voltage using US horn 846
CST voltage using horn
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Next step
Why all the previous work?
• Want to know: Level of inter-cable coupling in pedestal base.• What to do: Implement measures minimizing external energy entering
pedestal.• Constraints: Cost effective and practical.
![Page 11: Interface and cabling characterization for SKA Paul van der Merwe Prof. HC Reader Stellenbosch University](https://reader035.vdocuments.site/reader035/viewer/2022062318/55195768550346a5698b4631/html5/thumbnails/11.jpg)
Finally
• Best end and mid-span connections using current and field arguments.
• HF radiation measurements of cable tray structure. • Anechoic chamber and OATS measurements.• Pedestal and concrete base study. • Best interface.