ASSESSMENT OF SAR IN THE HUMAN HEAD, CAUSED BY MOBILE PHONE WITH MEASUREMENT OF THE EMITTED ELECTRIC FIELD RAD2012, 25-27 A PRIL 2012 - N IŠ, S ERBIA Branko

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


introduction equipment model for SAR assessment in which cases we use this model some advises for reducing radiation results and conclusion

INTRODUCTION


INTRODUCTION


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


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


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


reflection

absorption

transmission

Incident radiation

attenuation

ESTABLISHING EQUALITY BETWEEN EB AND ED


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


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


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


BASIC CALCULATIONS FOR THE PHANTOM


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


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


BASIC RESTRICTIONS FOR TIME VARYING ELECTRIC AND MAGNETIC FIELDS FOR FREQUENCIES UP TO 10

GHZ.


RADIATION PENETRATES

DEPENDING ON AGE


TIME DEPENDENCE OF TEMPERATURE DURING

TALK


PHASES OF RADIATION DURING THE USE OF

MOBILE PHONE


RESULTS AND CONCLUSION


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


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


Thank yu for your attention

ПРАШАЊА


SOME REMARKS


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]




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)





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


Affected part of

the head, taken

in consideration


Depth in

brain


Dura

Skull bone Cartilage Air

Skin


SIMULATING THE ATTENUATION FROM THE

HEAD TISSUES


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


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.


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:


SIMPLIFIED MODEL OF TISSUE LAYERS

Depth in

brain


Dura

Skull bone Cartilage Air

Skin


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


Plexiglas

Distilled water

Plexiglas

Air

Ed

Ein


mobile phoneairplexiglasdistilled waterdetector

ASSESSMENT OF SAR IN THE HUMAN HEAD, CAUSED BY MOBILE PHONE WITH

MEASUREMENT OF THE EMITTED ELECTRIC FIELD





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


Documents

ASSESSMENT OF SAR IN THE HUMAN HEAD, CAUSED BY MOBILE PHONE WITH MEASUREMENT OF THE EMITTED ELECTRIC FIELD RAD2012, 25-27 A PRIL 2012 - N IŠ, S ERBIA Branko