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: fisahn@ieee.org

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