ASSESSMENT OF SAR IN THE HUMAN HEAD, CAUSED BY MOBILE PHONE
WITH MEASUREMENT OF THE EMITTED ELECTRIC FIELD
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
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CONTENT
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
introduction equipment model for SAR assessment in which cases we use this model some advises for reducing radiation results and conclusion
INTRODUCTION
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
INTRODUCTION
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
The primary goal of this research is based on measurements of the emitted electric field (E) from mobile phone to assess the Specific Absorption Rate SAR, at some point in the brain of the user.To achieve this, it is necessary to establish such conditions that the field strength (E) before reaching the sensor of the instrument is weakened (by passage through a water phantom), as much as it would undermine the field passing through the tissues of head (skin, ear shell, skull bone, brain liquid) and reach the point at a depth of 2,5 mm in the human brain.The equation for transformation of the measured electric field E into the operational quantity SAR, in near field conditions, according the standard EN 50413, has the following shape:
whereσ - specific conductivity of brain tissue [S/m]
ρ - mass density of the brain tissue [kg/m3]
EQUIPMENT USED IN OUR STUDY
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Аntenna Coupler 4916 Freq. range 700MHz - 6GHz
Willtek Handheld Spectrum Analyzer 9102B Frequency range 100kHz – 4GHz
Willtek RF Shield 4921
MEANING OF NEAR- AND FAR-FIELD
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Reactive near-field region
Radiating near-field region
Far-field region
Lateral edge of the region, measured
from antenna0 to to +2D2/ +2D2/ to
E H No Quite Yes YesZ = E / H Z0 Z0 = Z0
Component to be measured
E & H E or H E or H
All measurements were performed in near-field region (900 MHz) = 0,33 m; (1800 MHz) = 0,17 m
“Because all the tissues in human body are non-magnetic (the relative permeability μr ≈ 1)” [6], although in the region of the near-filed both, magnetic and electric components of the electromagnetic field should be considered, conclusion is drawn that main contribution to SAR at RF, is from the interaction with the electric field. That is why, our assessment of SAR is made with analysis of the electric field.
INTERACTION OF ELECTROMAGNETIC
RADIATION WITH MATTER
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
reflection
absorption
transmission
Incident radiation
attenuation
ESTABLISHING EQUALITY BETWEEN EB AND ED
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Eb = Ed Eb – electric field strength at 2.5 mm depth in the brain; Ed – electric field strength at the detector’s surface.
Attenuationtissue = Attenuationphantom
- average relative dielectric constant
TISSUE DATA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Type of tissueBrain
ρ = 1040 kg/m3
Skull bone
SkinEar
cartilageBrain liquid
Dura AirEquivalen
t
Dielectric constants of each
tissueεrb σ [S/m] εrsb εrs εrc εrbl εrd εra
900 MHz 56,0 0,97 16,62 41,41 46,00 71,71 44,4 1 34,7
1800 MHz 43,5 1,15 15,56 38,8738,10
(1,9 GHz)67,2 42,9 1 30,6
Average thickness of each tissue [mm]
2,5 6,5 2 6 4 0,3 5 26,3
All data are valid for an average adult man
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
q(t) – antenna’s electrical charge in dependence of time;
Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution to the interaction with the radiation, the average dielectric constant of all these tissues can be calculated.
- average relative dielectric constant
BASIC CALCULATIONS FOR THE TISSUE
All contribution in tissue attenuation
PHANTOM MATERIAL DATA
Type of material Air Plexiglas Distilled water Equivalent
Relative dielectric
constants of each material
εra εrp εrw
900 MHz 1 2,63 78,2 34,7
1800 MHz 1 2,59 77,4 30,6
Thickness of each material [mm]
14 (900 MHz)16 (1800 MHz)
6(2 x 3 = 6)
15 (900 MHz)13 (1800 MHz)
35
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
BASIC CALCULATIONS FOR THE PHANTOM
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
rtf – distance between the mobile phone and the surface of the detector
All contribution in phantom attenuation
SPECIFIC CHARACTERISTIC OF THE INTENSITY OF THE
MOBILE PHONE RADIATION
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
By covering large areas of the phone with your hand, you reduce its ability to send and receive signals. The phone then increases its power and transmits stronger radiation to compensate this. So hold the phone as far down as possible, so it can operate at low power.
You can see the signal reception strength in the display. When reception is good, the phone reduces power and radiation. If reception is poor , the phone uses maximum power and radiation.
Hold it at he bottom
Get in the best position
DIFFERENT INTENSITY OF RECEIVED SIGNAL
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
BASIC RESTRICTIONS FOR TIME VARYING ELECTRIC AND MAGNETIC FIELDS FOR FREQUENCIES UP TO 10
GHZ.
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RADIATION PENETRATES
DEPENDING ON AGE
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TIME DEPENDENCE OF TEMPERATURE DURING
TALK
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
PHASES OF RADIATION DURING THE USE OF
MOBILE PHONE
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RESULTS AND CONCLUSION
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Results: In the case of optimal received signal of the tested mobile phones, assessed SAR values are close to the values that are declared by the manufacturers, for those mobile phones (valid for an ideal case). In case of weakening of the received signal by mobile phones (real situation), SAR values can be increased multiple times.
Conclusion: Possibilities of the measuring equipment and the applied mathematical model opens up the doors for the following research: •With change of the received signal for the tested phones, SAR assessment is made for many different situations in reality, for the same phone (in places where received signal of mobile phones is lower) . For such places SAR grows dramatically, due to its dependence on |Ei|
2. •With change of the attenuation factor (changes of the thickness of water phantom), it can be determined SAR for different depths in the brain or in any other tissue, •With accurately calculated SAR we can assess temperature increase at the point of measurement, located in brain tissue.
E is 3 to 4 times greater
REFERENCES
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
1. Guidelines for Limiting Exposure to Time-varying Electric, Magnetic and Electromagnetic Fields (up to 300 GHz), ICNIRP2. 50413 Basic Standard on Measurement and Calculation Procedures for Human Exposure to Electric, Magnetic and electromagnetic Fields (0 Hz – 300 GHz), European Committee for Standardization3. Elektromagnetizam I, II, Mirjana Jonoska4. FDTD Computation of Temperature Rise in the Human Head for Portable Telephones, Wang, J. and O. Fujiwara5. On Averaging Mass of SAR Correlating with Temperature Elevation due to a Dipole Antenna, A. Hirata, K. Shirai, and O. Fujiwara6. Interaction between mobile terminal antenna and user, Juho Poutanen7. SAR and Temperature Elevation in a Multilayered Human Head Model due to an Obliquely Incident Plane Wave, A. I. Sabbah and N. I. Dib8. SAR Estimation for Cellular Phone, Association of Radio Industries and Businesses9. Review of the scientific evidence for Limiting Exposure to EMFs (0–300 GHz), NRPB Britain
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Thank yu for your attention
ПРАШАЊА
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
SOME REMARKS
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Unlike the brain itself, “temperature elevation 0.2 K– 0.3 K in hypothalamus leads to altered thermoregulatory behavior” [5].
Acute RF heating (more than about 41-43 oC for 2-3 hours) can induce lens opacities (cataracts) in experimental animals. However, threshold for cataract induction resulting from chronic exposure to RF EMFs has not been defined. [9]
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
ПРОЦЕНА НА ДОЗА КАЈ НЕЈОНИЗИРАЧКОТО ЗРАЧЕЊЕ
Основни единициОсновни единици Единици заЕдиници за
јонизиречко зрачењејонизиречко зрачењеЕдиници заЕдиници за
не-јонизирачконе-јонизирачко зрачењезрачење
J/kg J/kg SvSv
ДозаДозаSASA
Специфична апсорпцијаСпецифична апсорпција
J/kg *1/тJ/kg *1/т W/kg W/kg Sv/тSv/т
Количина на дозаКоличина на дозаSASA//h SARh SAR
Количина на специфична Количина на специфична апсорпцијаапсорпција
За процена на количеството на апсорбираната енергија во човековото тело (дозата) потребно е де се дефинираат неколку клучни поими:
• Специфична енергетска апсорпција (ЅА): Се дефинира како апсорбирана енергија по единица маса биолошко ткиво изразена со џул врз килограм (J/kg). • Количина на специфична енергетска апсорпција (ЅАR): Се дефинира како
апсорбирана енергија по единица маса биолошко ткиво за одредено време, (W/kg).
• Густина на моќност (Ѕ): Кога моќност на зрачењето на рамен бран ќе помине низ единица површина нормална на правецот на движење на бранот. Се дефинира (W/m2)
SA(Jkg-1) = SAR (Wkg-1) * време на експозиција (секунди)
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution for each can calculate the average dielectric constant of all these tissues
SIMPLIFIED MODEL OF TISSUE LAYERS
Depth in
brain
CSF – liquor (brain liquid)
Dura
Skull boneEar
cartilageAir
Skin
26,3 mm
Eb Ein
The Heart's Electromagnetic FieldRAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Affected part of
the head, taken
in consideration
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Depth in
brain
CSF – liquor (brain liquid)
Dura
Skull bone Cartilage Air
Skin
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
SIMULATING THE ATTENUATION FROM THE
HEAD TISSUES
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Plexiglas
Distilled water
Plexiglas
Air
Ed
detector
Ein
35 mm
19 (21) mm
mobile phone
TISSUE DATA
Type of tissueBrain
ρ = 1040 kg/m3
Skull bone
SkinEar
cartilage
Brain liquid -
CSFDura Air
Equivalent
Relative dielectric
constants of each tissue
εrb σ [S/m] εrsb εrs εrc εrbl εrd εra
900 MHz 56,0 0,97 16,62 41,41 46,00 71,71 44,4 1 34,7
1800 MHz 43,5 1,15 15,56 38,87 38,10(1,9 GHz)
67,2 42,9 1 30,6
Average thickness of each tissue
[mm]
2,5 6,5 2 6 4 0,3 5 26,3
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
MEANING OF SAR
SAR – specific absorption rate [W/kg] Time derivative of the incremental electromagnetic energy (dW) absorbed by (dissipated in) an incremental mass (dm) contained in a volumen element (dV) of given mass density (ρ).
whereEi r.ms. value of the electric field strength in the tissue in V/m;σ conductivity of body tissue in S/m; ρ density of body tissue in kg/m3;ci heat capacity in body tissue in J/kg K;dT/dt time derivative of temperature in body tissue in K/s.
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Reactive near-field region Radiating near-field region
Far-field region
Lateral edge of the region, measured from antenna
0 to to +2D2/ +2D2/ to
E H No Quite Yes Yes
Z = E / H Zo Zo = Zo
Component to be measured E & H E or H E or H
Table below indicates the method at different distances from radio-stations:
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
SIMPLIFIED MODEL OF TISSUE LAYERS
Depth in
brain
CSF – liquor (brain liquid)
Dura
Skull bone Cartilage Air
Skin
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Еach layer of tissue that lies between mobile phone and brain have different relative dielectric constant. Based on their individual contribution for each can calculate the average dielectric constant of all these tissues
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Plexiglas
Distilled water
Plexiglas
Air
Ed
Ein
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
mobile phoneairplexiglasdistilled waterdetector
ASSESSMENT OF SAR IN THE HUMAN HEAD, CAUSED BY MOBILE PHONE WITH
MEASUREMENT OF THE EMITTED ELECTRIC FIELD
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
ВЗАЕМНОДЕЈСТВО НА ЕЛЕКТРОМАГНЕТНОТО ЗРАЧЕЊЕ СО МАТЕРИЈАТА
Апсорпција
Рефлексија
Трансмисија
Упаден зрак
Густина на моќност (Ѕ) (W/m2)
Количина на специфична енергетска апсорпција (ЅАR) (W/kg).
Aпсорбирана доза
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
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