1Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Cost 286 Workshop on„EMC 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: [email protected]
2Institut 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
3Institut 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 section non-leaky section
• System integration process requires detailed information about radiation and transmission behaviour and interference potential
4Institut 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)
5Institut 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
6Institut 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
7Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Setup (Attenuation)
Attenuation measurement at GEM, University of Hannover
21SD
• 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)
8Institut 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)
0 0.5 1 1.5 2 2.5
x 10-7
-50
0
50
100
150
200
Test pulse at output of leaky cable
t / s
U / V
0 0.5 1 1.5 2 2.5
x 10-7
-50
0
50
100
150
200
Test pulse at input of leaky cable
t / s
U / V
• Pulse shape nearly identical, merely amplitude damped
9Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (Transient Signal)
Comparison of the spectral energy distribution
106
107
108
109
10-12
10-10
10-8
10-6
Spectral energy distributionInput (---- 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
10Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (Transient Signal)
Radiation measurement with conical field probe
0 0.5 1 1.5 2 2.5 3
x 10-7
-100
0
100
200
300
Electrical field at leaky side
t / s
E(t) / (V/m)
0 1 2 3 4 5
x 10-7
-100
-50
0
50
100
Electrical field at back side
t / s
E(t) / (V/m)
• Electric field strength much higher on leaky side
11Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (Transient Signal)
Spectra of radiated electric field
0 2 4 6 8 10
x 108
0
1
2
3
4x 10
-10
f / Hz
|E(j)| / (V/m/Hz)
Electrical field at leaky side
0 2 4 6 8 10
x 108
0
1
2
3
4x 10
-10
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,...)
12Institut 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
13Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (CW-Signal, GTEM Cell)Circular radiation pattern via GTEM Cell measurement
-70 dB
-60 dB
-50 dB
-40 dB
30°
210°
60°
240°
90°
270°
120°
300°
150°
330°
180° 0°
Circular radiation pattern
900 MHz 1750 MHz5240 MHz
-70 dB
-60 dB
-50 dB
-40 dB
30°
210°
60°
240°
90°
270°
120°
300°
150°
330°
180° 0°
Circular radiation pattern at f = 1750 MHz
• Main lope in lower frequency range < 2 GHz• Radiation zeros occur in upper frequency range
14Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (CW-Signal, GTEM Cell)Circular radiation pattern via GTEM Cell measurement
0.2
0.4
0.6
0.8
1
30°
210°
60°
240°
90°
270°
120°
300°
150°
330°
180° 0°
Circular radiation pattern at f = 1750 MHz
-55 dB
-53 dB
-51 dB
-49 dB
-47 dB
-45 dB
30°
210°
60°
240°
90°
270°
120°
300°
150°
330°
180° 0°
Circular radiation pattern at f = 1750 MHz
• Linear and normalized scale shows good agreement with OATS measurements in frequency range < 2 GHz
15Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (CW-Signal, NF-Scan)
Field distribution along the cable
0 5 10 15 20 250
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5Electric Field Strength along the Cable at 1750 MHz
l in m
E in
V/m
0 5 10 15 20 250
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5Electric Field Strength along the Cable at 5240 MHz
l in m
E in
V/m
• Field strength along the cable decreases exponentially• High near field values in leaky sections• High attenuation in upper frequency range
16Institut für Grundlagen der Elektrotechnik und Messtechnik
Sven Fisahn
Measurement Results (CW-Signal, Attenuation)Attenuation measurement of cable with 35.7 m length
5.5 GHz
10 dB/
-100 dB
0 dB
MAGdB CH2 10 dB/ REF -20 dB
START 400 MHz STOP 6 GHz500 MHz/
CPL
FIL100100FIL100100
CAL
S21
á -20 dB
Date: 13.JAN.04 15:48:23
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
17Institut 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