Presentation on theme: "Kjell Hansson Mild Technical Description of Mobile Telephony System and Corresponding Exposure Levels Kjell Hansson Mild National Institute for Working."— Presentation transcript:
Kjell Hansson Mild Technical Description of Mobile Telephony System and Corresponding Exposure Levels Kjell Hansson Mild National Institute for Working Life, Umeå and Örebro University
Kjell Hansson Mild Biological effects of radiofrequency electromagnetic fields Thermal effects Rather well investigated, associated with acute exposure, threshold values. Guidelines and limits exists, epidemiology is missing in general. Non thermal effects Data exists on such effects, unclear if these effects also constitutes a health hazard, more research is needed on this.
Kjell Hansson Mild Specific Absorbtion Rate, SAR How much energy that is absorbed per unit time and unit mass SAR is given as watt/kg, W/kg
Kjell Hansson Mild 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
Kjell Hansson Mild Cataract need about 100 W/kg The eye is about 10 gr Safety factor 10 gives SAR 10 W/kg over 10 g contiguous tissue General public extra 5 times local SAR = 2 W/kg. This is what we call guidelines for mobile phones.
Kjell Hansson Mild ANSI / IEEE / FCC SAR < 0.4 W/kgOccupational exposure SAR < 0.08 W/kgGeneral public Part of body: Max inhomogeneity 1:20 SAR < 8 W/kg Occupational exposure SAR < 1.6 W/kg General public 1 gram tissue
Kjell Hansson Mild GSM 900 Pulsed output power max 2W Down regulation in steps to 3 mW Duty cycle 1/8 gives max mean power 0.25 W and low mean 0.4 mW DCS 1800 Peak pulse power max 1 W, low 2 mW Max mean power W, low mean 0.25 mW With DTX system further reduction
Kjell Hansson Mild DECT 1900 MHz, peak power 250 mW, 100 Hz rep. rate Duty cycle 1/24, mean power about 10 mW
Kjell Hansson Mild
Overall SAR maximum (W/kg) for the power distribution calculated for a continuous output of 0.25 W.
Kjell Hansson Mild GSM900 Antenna Loss Relative 2W Reference Dipole With Sim. Hand Without Hand Loss Due to Hand Mean=2.64 Std=1.77
Kjell Hansson Mild With Sim. Hand Without Hand Loss Due to Hand Mean=1.90 Std=1.37 dB
Kjell Hansson Mild 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.
Kjell Hansson Mild Electric field strength V/m
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 < and 13.4 mW/m 2 (max 0.28% of ICNIRP) Median value 0.01 mW/m 2 Max sum of all levels in the bands: < and 47.6 mW/m 2, median 0.2 mW/m 2 ICNIRP values: 900 MHz4.5 W/m MHz9.0 W/m 2