presentation bioem 2005
TRANSCRIPT
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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, [email protected]
**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: [email protected]
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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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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
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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