Jafar Keshvari Chairman, International Electrotechnical Commission IEC MT1 (IEC 62209-1 & IEC 62209-2) SCIENTIFIC BASIS OF THE COMPLIANCE ASSESSMENT of.

Jafar KeshvariChairman, International Electrotechnical Commission

IEC MT1 (IEC 62209-1 & IEC 62209-2)

SCIENTIFIC BASIS OF THE COMPLIANCE ASSESSMENT

of PORTABLE WIRLESS DEVICES

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Outline__________________________________________

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• Background & Historical review

• Ionizing and non-ionizing radiation

• EMF exposure standards

• Why to develop RF compliance standards

• RF measurement/assessment standards in International Electro-technical Commission (IEC)

• Future of IEC wireless devices compliance standards

• Along the history, philosophers and scientists have explored and developed several natural phenomena that facilitated the life of the humankind.

• The philosopher Thales of Milteus (640-546 B.C) is thought to have been the first person who observed the electrical properties of amber and explored the magnetic properties of lodestone.

• The twitch of the leg of a dead frog when dissected with a moisted metal scapel that has been noticed by Galvani in 1786, had led Volta to invent the electric battery .

• Armstrong demonstrated FM radio transmission in 1933.

• Advanced communications and telecommunications infrastructure have reduced transportation needs, led to reduction of fuel consumption and consequently reduction of air pollution from carbon monoxide, carbon dioxide, nitrogen oxides, hydrocarbons and other pollutants.

Background & Historical review__________________________________________

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• Electromagnetic Radiation: consists of waves of electric and magnetic energy moving together through space.

• All electromagnetic radiation can be classified by frequency from the extremely low to extremely high frequencies.

• Extremely high frequency radiation such as Ultraviolet (UV) and X-rays is called “Ionizing Radiation” because it is powerful enough to effect changes in the atoms of matter it strikes, by breaking chemical bonds (ionization) , thus altering their chemical and biological nature .

• Electromagnetic radiation at those frequencies below the UV band are generally classified as “Non-Ionizing Radiation” because they typically lack the energy to effect changes in atomic structure.

Background & Historical review…__________________________________________

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The Electromagnetic Spectrum

• Non-ionizing radiation, when incident on matter, is incapable of liberating electrons (i.e. ionizing) from atoms and molecules.

• There is a minimum quantum energy below which a radiation would be unable to bring about ionization. The quantum energy, E, of radiation is given by:

E = Ћf

where f and Ћ denote frequency of radiation and Plank’s constant respectively.

• For minimum ionization energy of 12 electron volts (eV), since h = 4.1357e-15 eV.s, the minimum frequency of radiation would be around 2.9e15 Hz (2900 TeraHz). This corresponds to a wavelength of about 1.034e-07m or 103.4nm. This lies near the lower wavelength-edge of the Ultraviolet (UV) spectrum

• Energy quanta of RF far below level needed to break chemical bonds in DNA

Background & Historical review (Ionizing and non-ionizing radiation

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Non-ionizing radiation wavelengths and frequencies

λ/ƒ

ULTRAVIOLET

VISIBLE LIGHT

INFRARED

MW&RF

UVC**

UVB**

UVA**

(λ ) Wave-length,

200* –

280nm

280 –

315nm

315 –

400nm

400 –

780nm

780nm–

1mm

1mm-

30km

(ƒ) Fre-

quency

1500 – 1071TH

z

1071–

952THz

952 –

750THz

750 –

385THz

385THz-

300GHz

300GHz-

10kHz

** WHO (World Health Organization) classification of the non-ionizing UV spectrum. * 100nm as per the International Commission on Illumination.


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• Wirless communication devices operates at frequencies 100-6000 MHz.

• Mobile phones operate at a variety of frequencies between about 800 and 2200 MHz.

• Mobile Phones base station antennas emit EMR in the range 1800 – 2000 MHz

• Computer monitors emit a broad range of EMR from 30 Hz up to 300 GHz.

• Electromagnetic waves may produce biological effects which may sometimes, but not always, lead to adverse health effects. It is important to understand the difference between the two:

• A biological effect occurs when exposure to electromagnetic waves causes some noticeable or detectable physiological change in a biological system.

• An adverse health effect occurs when the biological effect is outside the normal range for the body to compensate, and thus leads to some detrimental health condition.


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• Does fast evolving Communications and Information Technologies has negative Impacts on health and Environment:

• The electromagnetic exposure associated with equipment use?

• Equipment waste disposal?

Leave the answer to you, rather focus on:

• How to evaluate the energy absorption in the human body caused by electromagnetic expsoure


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Wireless technology RF Sources_________________________________________________________

Exposure to common EMF sources__________________________________________

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• The quantification challenge of RF interaction with human body?

• Micro and micro approach?

• The dimension of the wave is much larger than the human body.

• The dimension of the wave is much smaller than the human body.

• The dimension of the wave is about the same size as the human body.

RF-human body Interaction analysis?__________________________________________

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Low-frequency electric and magnetic fields

f = 0 - 30 kHz= – 10 km

Currents

Surface charge

Electric fieldMagnetic field

Circulatingcurrents

Radiowave

Heating

Radio frequency electromagnetic fieldsf = 30 kHz – 300 GHz

= 10 km – 1 mm

Optical radiationf = 300 GHz-1000 THz

= 1 mm – 100 nm

Heating, photochemical reactions

DermisEpidermis

Optical radiation

How to quantify RF energy absorption, SAR

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2ESAR (σ ωε') (W/kg)

ρ

For sinusoidal EM fields, the time rate of energy deposited in a small volume is defined as Specific Absorption Rate:

σ and ε’ indicate how much energy will be absorbed by the material

The power absorbed per unit mass of tissue is referred to as Specific Absorption Rate (SAR).

Permittivity ε:Describes how much induced polarization and

partial alignment of permanent electric dipoles occures for a given applied electric field E

Conductivity σ:How much conduction current density will be

produced by a given applied E.

EMF EXPOSURE STANDARDS __________________________________________

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• ICNIRP

• guidelines developed by a committee of appointed experts, no industry members

• ICNIRP’s guidance is equally applicable to both base stations, phones and other radio transmitting equipments

• closed meetings • Endorsed by WHO

• A biological effect occurs when exposure to electromagnetic fields causes some noticeable or detectable physiological change in a biological system.

• An adverse health effect occurs when the biological effect is outside the normal range for the body to compensate.

• In the RF region thermal effects are the stablished harmfull effect

• Only replicated studies can be a scietific basis of expsoure standards.

• Identified behavioural changes i.e. a rise in whole body temperature in excess of 1°C at a Specific Energy Absorption Rate (SAR) of 1- 4w/kg.

Rationale behind limits for human RF exposure in International Commission for Non-Ionizing Radiation Protection

(ICNIRP) guidelines__________________________________________

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• Limits are given for whole body SAR and localized SAR to prevent excessive tissue heating due to RF exposure

• Limit for whole body SAR is based on a threshold of 4W/kg (corresponds to about 1°C body temperature rise). Safety factors 10 and 50 are used for occupational and general public exposure respectively

• The rationale for local SAR limit and averaging mass is implicitly based on exposure effects (thermal) on eye with a safety factor of 50

RF exposure limits and safety margins

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Exposure from mobile phone

• SAR non-uniform (local SAR value usually below 1 W/kg in 10 g tissue mass)

• Temperature more uniform

• Equilibrium local temperature increase is <0.2 °C at maximum

T in head (10 g average mass, antenna average emitted power of

0.25 W)

ICNIRP: threshold-based

Established health effects

Reduction factors

Threshold of established health effects

Exposure limit

Exp

osu

re

high

low

Source: ICNIRP

ICNIRP basic restrictions on exposure on the frequency range 10MHz to 10GHz

TissueRegion

SAR LimitW/kg

AverageParameters

Occupational GeneralPublic

Mass(g)

Time(mins)

WholeBody

0.4 0.08 - 6

Head andTrunk

10 2 10 6

Limbs 20 4 10 6

Flux of electromagnetic energy______________________________________

EMF source Approximate energy flux (watts/square meter)

Sunlight at the earth's surface at noon 1350 W/m2

Infrared heat radiation from a living person

20 W/m2

Mobile base station 70 W/m2 – 3 mW/m2 a)

Microwave emission from a living person

3 mW/m2

a) 30 – 2000 MHz, Göteborg and various sites, Sweden (Uddmar T, Thesis, Chalmers U., 1999)

ICNIRP limit 4.5 W/m2 at 900 MHz

Introduction: Measurement and Computational standards

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• All portable wireless devices have to comply with RF exposure limits before putting them in the market.

• Compliances standards for the portable RF wireless devices were developed by International Electrotechnical Commission IEC and IEEE mainly relevant to the mobile phones [IEC-62209-1 2005, IEEE-1528, 2003].

• The merge of new technologies and different usage positions of the mobile devices led to development of relevant compliance standard to cover the exposure evaluation of the other parts of the body other than the head [IEC-62209-2, 2010].

• Although the SAR was established at the highest certified level, the actual SAR level for the mobile phone during use is generally much lower than the maximum values. In fact, since mobile phones are designed to operate at many different power levels, they only use the minimum level of power required to provide a connection to the network. In theory, the closer you are to a base station antenna, the lower the power level required by the mobile phone.

RF compliance assessment standards______________________________________• Compliance can be assessed through measurements or

calculations.

• There is no meaning for existence of exposure Guidelines/standards if it is not possible to measure it.

• Practically it is not possible to measure the energy absorption in the body of living humans!

• In order to assess the exposure limits there has to be standardized procedures to evaluate those limits.

There is a need to develop phantoms head/body phantoms

• Advanced instrumentation is needed for this purpose

• Accurate procedure with well defined and quantified uncertainty is needed.

International Electro-technical Commission (IEC)

Wireless devices RF Assessment Standards

______________________________________ • IEC-MT62209, - Part 1, SAR for handsets. To revise the

standard IEC62209-1: “Procedure to Measure the Specific Absorption Rate (SAR) for Hand-Held Mobile Telephones in the Frequency Range of 300 MHz to 3 GHz” by the end of 2011.

- Part 2, SAR for other handheld and body worn devices. To revise the IEC62209-2: “Procedure to determine the specific absorption rate (SAR) for wireless communication devices used in close proximity to the human body (frequency range of 30 MHz to 6 GHz) standard by 2013.

- To unify IEC62209 part 1 & 2 standards by 2013.

SAMHead phantom Field measurement unit

• the Standard Anthropomorphic Model - is a head shell phantom intended primarily for use in the measurement of exposure from mobile phones (or other hand-held transmitters)

• SAM is defined as standard phantom allowing a conservative measure of the radio exposure of people of all origins and all ages. The ear region is defined with reference points and planes to facilitate reproducible positioning of telecommunications devices.

• The dimensions of a 90th percentile male head were selected for the phantom.

• IEC, CENELEC, and IEEE have developed standard procedures for assessing exposures from mobile phones which specify the use of a SAM phantom.

•

SAM head phantom______________________________________

Device under test Tissue simulating liquid

Mobile phone exposure assessment__________________________________________

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Thank you!

Questions?

Jafar Keshvari Chairman, International Electrotechnical Commission IEC MT1 (IEC 62209-1 & IEC 62209-2) SCIENTIFIC BASIS OF THE COMPLIANCE ASSESSMENT of.

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