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Presentation – BIOEM 2005

EXPOSURE SYSTEM FOR SIMULATING GSM AND WCDMA MOBILE PHONE USAGE

A. Bahr*, H. Dorn**, T. Bolz**IMST, Kamp-Lintfort, Germany, achim.bahr@imst.de

**Charité – Universitätsmedizin Berlin, Germany

This work was funded by the Federal Office for Radiation Protection (BfS) within the German mobile telecommunication research (DMF) program

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Overview

• Objective

• Exposure setup block diagram

• Exposure signals

• Antenna solution

• Dosimetry

• SAR results

• Conclusion

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Objective of the Study

• DMF study „Investigation of volunteers exposed to electromagnetic fields of mobile phones“

• Analysis of possible effects on brain activity in sleep and waking

• Wake outcome variables• Spontaneous EEG

• Evoked and event related potentials

• Cognitive functions

• Sleep outcome variables• Classical sleep parameters

• Quantitative parameters derived from the raw data

Contact point: heidi.danker-hopfe@charite.de

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Block Diagram of the Exposure Setup

GSM

WCDMA

GSM

WCDMA

• Computer controlled double blind protocol

• GSM, WCDMA and sham exposure (isolation >80 dB)

• Permanent monitoring of power levels

• Alarm generation and auto-switch-off in case of malfunctions

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Exposure Signal Characteristics

GSM:

• 900 MHz

• Pulse modulated carrier

Ton Toff

Ton = 553 µsToff = 4,062 ms

t

s(t)

Ton Toff

Ton = 553 µsToff = 4,062 ms

t

s(t)

WCDMA:

• Signal generation according to [Mbonjo, 2004]

• 1966 MHz QPSK signal with fast power control

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State of the Art Antenna Solutions

Exposure setups simulating mobile phone usage

• Commercially available mobile phone [Lee, 2003]

• Patch antennas in a wooden mount [Huber, 2000]

• Quasi-far-Field [Borbély, 1999]

• Body worn antenna [Schmid, 2004]

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Antenna Specs and Intended Use Position

Specifications:

• Localized exposure

• GSM and WCDMA coverage

• Exposure times of 8 hours during day and night

Dual band antenna surrounding the pinna

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Antenna Details

1 mm

110 mm40 mm

1 mm

110 mm40 mm

-30,0

-25,0

-20,0

-15,0

-10,0

-5,0

0,0

500 1000 1500 2000 2500

f [MHz]

s11 [

dB]

• PCB with a PIFA type radiator

• PCB covered by foam and a washable textile cover

• Weight: 14 g

• Total thickness: 4 mm

• Free space reflection coefficient:

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Measurement Method

• DASY4 system

• Tissue simulating liquids according to FCC requirements

• SAM head inappropriate because of collapsed pinna

• Measurements in the flat section of SAM phantom

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Simulation Method

• Empire™ software

• Based on FDTD

x

yα

• Heterogeneous Visible human head model (AFRL)

• Antenna is directly placed at the head model

• FDTD grid terminated with 6 layer PML

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900 MHz Flat Phantom SAR Results

Measurement Simulation

• No experimental artifacts due to antenna feeding cable

• Widespread SAR distribution

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1966 MHz Flat Phantom SAR Results

Measurement Simulation

• SAR maximum near the radiating element

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10

15

20

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SAR_1g SAR_10g SAR_1g SAR_10g

900 MHz 1966 MHz

SAR

[W/k

g]MeasurementSimulation

Flat Phantom Localized SAR Values

• 1 W antenna input power

• 22 % max. difference measurement/simulation

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x

yα

Visible Human Localized SAR Values

• 1 W antenna input power

• 28 % max. positioning dependency

0

5

10

15

20

25

30

SAR_1g SAR_10g SAR_1g SAR_10g

900 MHz 1966 MHz

SAR

[W/k

g]

Original positionAlpha+15°Increased head distance: +2 mm

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Conclusion

• Development and Characterization of a GSM and WCDMA exposure system simulating mobile phone usage

• Computer controlled double blind protocol

• Permanent monitoring and auto-switch-off in case of malfunctions

• Low weight and thin planar dual band antenna• Localized exposure

• Enabling 8 hours exposure time during day and night

• Reasonable SAR sensitivities due to changes in antenna positioning