ITU-T Technical Session on EMF

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 ITU-T Technical Session on EMF
Comparison between measurement and
calculationsEMF-estimator, K.guide

• Fryderyk Lewicki
• ITU-T SG5, Rapporteur for Q 3/5

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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

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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

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Measurement

• Example of the result of the frequency selective
  measurement

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Measurement

• Example of the result
• of the frequency selective measurement

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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)

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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

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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

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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

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Calculations

• Very easy but with big overestimation isotropic
  source with maximum ERP
• Far field model
• Synthetic model On the right example of the
  vertical cross-section

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Calculations

• Full-wave models (MoM, FDTD etc.)
• Accuracy of calculation depends on the model used
  and on the exactness of description of
  transmitting antennas

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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

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Calculationsadvantages

• Non existing radiating sources can be considered
• The possibility to take into account the maximum
  possible radiation levels (ERPs) 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

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Calculationsadvantages

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

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Calculations advantages
VHF TV (ERP125kW, h90m), FM (total ERP423kW,
h55m), GSM900 (ERP1080W, h30m), GSM1800
(ERP1120W h30m) Cumulative exposure V/m
Vertical cross-section, azimuth 333
Horizontal cross-sections h90 m h55 m h30 m
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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
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Comparisonmeasurement vs. calculation

• Good agreement if properly done

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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

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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

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Resolution 72
Measurement concerns related to human exposure to
electromagnetic fields

• Recommendation ITU-T K.guide Guidance on how to
  manage humane exposure to EMFs will be written
  with Resolution 72 taken into account
• Current Technical Session on EMF is an example
  of action in accordance with Resolution 72

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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

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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

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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

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Conclusions

• 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
  

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Thank youQuestions, Comments?