1 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Fisahn 1, Michael Camp 1, Núria Riera Díaz 2, Robert Kebel 3, Heyno Garbe 1 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

2 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 leaky sectionnon-leaky section System integration process requires detailed information about radiation and transmission behaviour and interference potential

4 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 S 21 (transfer function of the cable and the connectors at each end)

8 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn Measurement Results (Transient Signal) Transmission measurement Fast transient pulses (rise time 5 ns) with double exponential character (cable length 10 m) Test pulse at output of leaky cable t / s U / V Test pulse at input of leaky cable t / s U / V Pulse shape nearly identical, merely amplitude damped

9 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn Measurement Results (Transient Signal) Comparison of the spectral energy distribution Spectral energy distribution Input (---- blue) Output (---- red) |U(j )| / (V/m/Hz) f / Hz Identical characteristics of both spectra Pulse shape nearly unaffected by transmission through leaky section cable

10 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn Measurement Results (Transient Signal) Radiation measurement with conical field probe Electrical field at leaky side t / s E(t) / (V/m) Electrical field at back side t / s E(t) / (V/m) Electric field strength much higher on leaky side

11 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn Measurement Results (Transient Signal) Spectra of radiated electric field f / Hz |E(j )| / (V/m/Hz) Electrical field at leaky side f / Hz |E(j )| / (V/m/Hz) Electrical field at back side Spectral energy distribution < 1 GHz reduced Spectral energy distribution > 1 GHz very similar Discrete frequencies (75 MHz, 150 MHz, 225 MHz,...)

12 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn Measurement Results (CW-Signal, GTEM Cell) Circular radiation pattern via GTEM Cell measurement Main lope in lower frequency range < 2 GHz Radiation zeros occur in upper frequency range

14 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 < 2 GHz

15 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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 < 1 GHz larger than 50 dB in freq. range > 3.5 GHz

17 Institut für Grundlagen der Elektrotechnik und Messtechnik Sven Fisahn 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