Post on 27-Mar-2015
Kjell Hansson Mild
Technical Description of Mobile Telephony System and
Corresponding Exposure Levels
Kjell Hansson Mild
National Institute for Working Life, Umeåand
Örebro University
Kjell Hansson Mild
Biological effects of radiofrequency electromagnetic fields
Thermal effectsRather well investigated, associated with acute exposure, threshold values. Guidelines and limits exists, epidemiology is missing in general.
Non thermal effectsData exists on such effects, unclear if these effects also constitutes a health hazard, more research is needed on this.
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Specific Absorbtion Rate, SAR
How much energy that is absorbed per unit time and unit mass
SAR is given as watt/kg, W/kg
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ICNIRP / EU
Not wanted effects for SAR > 4 W/kg
Safety factor 10 for occup exposed,gives whole body limit of
SAR < 0.4 W/kg
For general public an additional factor 5,
SAR < 0.08 W/kg
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Cataract need about 100 W/kgThe eye is about 10 gr
Safety factor 10 givesSAR 10 W/kg over 10 g contiguous tissue
General public extra 5 timeslocal SAR = 2 W/kg.This is what we call ”guidelines for mobile phones” .
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ANSI / IEEE / FCC
SAR < 0.4 W/kg Occupational exposureSAR < 0.08 W/kg General public
Part of body: Max inhomogeneity 1:20
SAR < 8 W/kg Occupational exposureSAR < 1.6 W/kg General public
1 gram tissue
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GSM 900Pulsed output power max 2WDown regulation in steps to 3 mWDuty cycle 1/8 gives max mean power 0.25 W and low mean 0.4 mW
DCS 1800Peak pulse power max 1 W, low 2 mWMax mean power 0.125 W, low mean 0.25 mW
With DTX system further reduction
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DECT
1900 MHz, peak power 250 mW, 100 Hz rep. rate
Duty cycle 1/24, mean power about 10 mW
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SARSpecific Absorption Rate (W/kg)
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peak 1 g any 1 g cube 10 g any 10 g cube4.0 2.22 1.53 1.66 0.91
Van Leeuwen et al, TNO report FEL-99-C128, 1999
Overall SAR maximum (W/kg) for the power distribution calculated for a continuous output of 0.25 W.
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GSM900 Antenna Loss Relative 2W Reference Dipole
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70
Tested Handsets
dB
With Sim. Hand
Without Hand
Loss Due to Hand Mean=2.64 Std=1.77
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GSM1800 Antenna Loss Relative 1W Reference Dipole
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
1 3 5 7 9
11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
Tested Handsets
d
With Sim. Hand
Without Hand
Loss Due to Hand Mean=1.90 Std=1.37
dB
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Mobile Phone Base Stations
Power balance between base station and handheld terminal
No need to use more power than the phone can send back!
However, since the base has better receiving antenna slighty more power is used by the base station than the phone.
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Electric field strength V/m
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Kjell Hansson Mild
Mobile Phone Base Stations
Short term mission within COST 244bis
346 measurements in five countries of GSM 900 and GSM 1800 bands
Power density at single frequencies varied between< 0.000001 and 13.4 mW/m2 (max 0.28% of ICNIRP)Median value 0.01 mW/m2
Max sum of all levels in the bands:<0.000001 and 47.6 mW/m2, median 0.2 mW/m2
ICNIRP values: 900 MHz 4.5 W/m2
1800 MHz 9.0 W/m2