ITU-T Technical Session on EMF

ITU-T Technical Session on EMFGeneva, 27 May 2009

InternationalTelecommunicationUnion

ITU-T Technical Session on EMF

Fryderyk LewickiITU-T SG5, Rapporteur for Q 3/5

Comparison between measurement and calculations

EMF-estimator, K.guide



Introduction

Human exposure assessment is in responsibility of the ITU-T SG5, Question 3

ITU-T has prepared in this subject the following Recommendations:

K.52 (2000/2004), K.61 (2003/2008) K.70 (2007) K. guide – under development



Measurement

SAR measurement human head phantom and

automatic system very important for the hand sets

manufacturers

Electric field strength measurement

broad band – cheap but with overestimation

frequency selective – more expensive and time consuming, require post processing

On site and laboratory



Measurement

Example of the result of the frequency selective measurement



Measurement

Example of the result

of the frequency selective

measurement



Measurementadvantages

It takes into account all radiating sources with real parameters

It takes into account real environment (reflections, antenna supporting hardware, obstacles)

Takes into account simultaneous exposure in the real way (phase differences of the different waves are taken into account)



Measurementadvantages

It can be done with little knowledge about radiating sources (initial measurement of the occupied spectrum is required only)

Good quality measurement equipment is accessible on the market

A life demonstration of the measurement to the interested people is possible



Measurementdisadvantages

Measurement is not possible for the radiating sources that do not exist yet

It is difficult to take into account the time variation of the EMF (for example mobile communication)

The effect of the presence of staff and equipment on the EMF distribution has to be avoided

SAR measurements have to use phantoms that are approximations only of the human body



Measurementdisadvantages

It is difficult to confirm and check that all the sources are operating with maximum ERP

In the multiple sources environment a post processing is required because of different limits for different operating frequencies

There is no probe covering the whole required frequency range,

Out of band emissions may lead to overestimation in the in-band measurement



Calculations

Very easy but with big overestimation – isotropic source with maximum ERP

Far field modelSynthetic model –

On the right: example of the vertical cross-section



Calculations

Full-wave models (MoM, FDTD etc.)Accuracy of calculation depends on the

model used and on the exactness of description of transmitting antennas



Simultaneous exposure to multiple sources

Typical situation is presented on this chart. Radiation from the broadcasting Transmitting Stations gives higher levels then mobile Base

Stations



Calculationsadvantages

Non existing radiating sources can be considered

The possibility to take into account the maximum possible radiation levels (ERP’s) that lead to the maximum possible exposure levels

There are many calculation methods with different level of accuracy

The calculation with high level of overestimation is very easy to use



Calculationsadvantages

Calculation costs are lower then the cost of measurementsIt gives an opportunity to use mitigation technique if requiredIt is possible to make calculation in areas with no access



Calculations advantages

VHF TV (ERP=125kW, h=90m), FM (total ERP=423kW, h=55m), GSM900 (ERP=1080W, h=30m), GSM1800

(ERP=1120W h=30m) Cumulative exposure [V/m]

Horizontal cross-sections: h=90 mh=55 mh=30 m

Vertical cross-section, azimuth 333°



Calculationsdisadvantages

Very accurate results require detailed description of the radiating antennas

In most cases do not take into account the influence of reflections

Require good knowledge of the software used

Require at least basic knowledge concerning transmitting antennas

FEKO software



Comparisonmeasurement vs. calculation

Good agreement if properly done



Measurement vs. Calculations

Human exposure assessment may be done by measurement or calculations

Both methods have advantages and disadvantages

Both methods have similar level of uncertainty and accuracy depending on the method and equipment or software used



Resolution 72 Measurement concerns

related to human exposure to electromagnetic fields

Recognizing that some publications about EMF

effects on health create doubt among the

population, in particular in developing countries

Resolves to invite ITU-T, in particular Study

Group 5, to expand and accelerate its work and

support

Invites to contribute actively to the work of

Study Group 5, in providing relevant and timely

information, in order to assist the developing

countries by providing information and

addressing measurement concerns related to RF

exposure



Resolution 72

Measurement concerns related to human exposure to electromagnetic fields

Recommendation ITU-T K.guide

„Guidance on how to manage humane

exposure to EMF’s” will be written with

Resolution 72 taken into account

Current Technical Session on EMF is an

example of action in accordance with

Resolution 72



ITU-T Recommendation K.guide

Guidance on how to handle the problem of the human exposure assessment in order to help the user to apply existing standards

procedures how to evaluate exposure

by measurement by calculations

procedures how to show the compliance with exposure limits

this Recommendation will be written in the possibly simple way and in order to be easy to understand



ITU-T Recommendation K.guide

It will include examples of the results of measurements

broad band frequency selective

examples of evaluation of the exposure levels around typical radiation sources:

mobile base stations broadcasting transmission stations wireless access systems

examples of compliance evaluation for the typical cases of simultaneous exposure to multiple sources of radiation



Recommendation ITU-T K.70

Mitigation techniques to limit human exposure to EMFs in the vicinity of radiocommunication stations

Modeling of the transmitting antennas Importance of the

Vertical Radiation Pattern (VRP) Identification of the

main source of radiation Mitigation techniques in

order to reduce radiation level – if required EMF-estimator –

software with the library of the examples of transmitting antennas



ITU-T SG5 takes part in standardization by

preparing Recommendations which give

appropriate guidance for administrations and

telecommunication operators and supports

developing countries (Resolution 72)

ITU activity is complementary to the works carried

out in other international standardization entities

involved in this subject

Conclusions



Thank you

Questions, Comments?

ITU-T Technical Session on EMF

Documents

Transcript of ITU-T Technical Session on EMF