Cost 286 Workshop on

1
Cost 286 Workshop onEMC Aspects of Wireless
Communications in Transport Systems
Analysis of Leaky Section Cables for Multi-Band
Aircraft Cabin Communications with different
Measurement Techniques Sven Fisahn1, Michael
Camp1, Núria Riera Díaz2, Robert Kebel3, Heyno
Garbe1 1 Institut für Grundlagen der
Elektrotechnik und Messtechnik, Universität
Hannover 2 Institut für Kommunikation und
Navigation, Deutsches Zentrum für Luft- und
Raumfahrt 3 Lightning Protection and
Electromagnetic Compatibility, Airbus Deutschland
GmbH e-mail fisahn_at_ieee.org
2
Analysis of LSC by Measurement

• Leaky Section Cable (LSC)
• Measurement Setup
• Open Area Test Site (OATS)
• GTEM Cell Measurement
• Near Field Scanning
• Attenuation Measurement
• Measurement Results
• Transient Signal (Near Field Scanning,
  Attenuation)
• CW-Signal (OATS, GTEM Cell, Attenuation)
• Summary

3
Leaky Section Cable (LSC)

• Enable use of portable electronic devices (PEDs)
  inside cabin (e.g. laptops, mobile phones)
• Antennas for multi-band aircraft cabin
  communications (e.g. WLAN, GSM, UMTS, DECT
  X2X) required
• LSC functions both as a transmission line and as
  an antenna

• System integration process requires detailed
  information about radiation and transmission
  behaviour and interference potential

4
Measurement Setup (Open Area Test Site)

• DLR test site in Oberpfaffenhofen (Germany)
• Circular far field radiation pattern
• Vertical and horizontal polarization
• CW-signals (700 MHz to 2.5 GHz)

5
Measurement Setup (GTEM Cell Measurement)

• GTEM 1250 at GEM, University of Hannover
• Circular near field radition pattern
• CW-signals (450 MHz to 6 GHz)
• cable length 1 m, includes 1 leaky section

6
Measurement Setup (Near Field Scanning)

• Near field measurements at GEM, University of
  Hannover
• Distribution of electric field strength along the
  cable
• ? CW-signals (450 MHz to 6 GHz)
• Radiation at front side and back side of LSC
• ? Transient signals (rise time 5 ns)
• Conical and biconical field probes

7
Measurement Setup (Attenuation)

• Attenuation measurement at GEM, University of
  Hannover

• Transmission behaviour
• CW-signals (450 MHz to 6 GHz)
• Measurement setup
• Cable is unrolled and positioned on the concrete
  floor of the laboratory
• Scattering parameter S21 (transfer function of
  the cable and the connectors at each end)

8
Measurement Results (Transient Signal)

• Transmission measurement
• Fast transient pulses (rise time 5 ns) with
  double exponential character (cable length 10 m)

• Pulse shape nearly identical, merely amplitude
  damped

9
Measurement Results (Transient Signal)

• Comparison of the spectral energy distribution

• Identical characteristics of both spectra
• Pulse shape nearly unaffected by transmission
  through leaky section cable

10
Measurement Results (Transient Signal)

• Radiation measurement with conical field probe

• Electric field strength much higher on leaky side

11
Measurement Results (Transient Signal)

• Spectra of radiated electric field

• Spectral energy distribution lt 1 GHz reduced
• Spectral energy distribution gt 1 GHz very similar
• Discrete frequencies (75 MHz, 150 MHz, 225
  MHz,...)

12
Measurement Results (CW-Signal, OATS)

• Circular radiation pattern via OATS
• Four distances d from the cable axis at 2 GHz

• Single and wide main lope for parallel
  polarization
• Zeros at 0 and 180 deg. for perpendicular
  polarization

13
Measurement Results (CW-Signal, GTEM Cell)

• Circular radiation pattern via GTEM Cell
  measurement

• Main lope in lower frequency range lt 2 GHz
• Radiation zeros occur in upper frequency range

14
Measurement Results (CW-Signal, GTEM Cell)

• Circular radiation pattern via GTEM Cell
  measurement

• Linear and normalized scale shows good agreement
  with OATS measurements in frequency range lt 2 GHz

15
Measurement Results (CW-Signal, NF-Scan)

• Field distribution along the cable

• Field strength along the cable decreases
  exponentially
• High near field values in leaky sections
• High attenuation in upper frequency range

16
Measurement Results (CW-Signal, Attenuation)

• Attenuation measurement of cable with 35.7 m
  length

• Attenuation of LSC
• increases towards higher frequencies
• about 12 dB in frequency range lt 1 GHz
• larger than 50 dB in freq. range gt 3.5 GHz

17
Summary

• Motivation for investigations of LSC
• Principle build up of leaky section cable (LSC)
• Measurement techniques
• Open area test site (OATS)
• GTEM cell measurement
• Near field scanning
• Attenuation measurement
• Measurement results
• Transient signal
• CW-signal