ITU-T
Technical Session on EMF
Comparison between
measurement and calculations
EMF-estimator, K.guide
Fryderyk Lewicki
ITU-T SG5, Rapporteur for Q 3/5
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
Example of the result of the frequency selective measurement
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
Example of
the result
of the
frequency
selective
measurement
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
advantages
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)
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
advantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
disadvantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Measurement
disadvantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Calculations
Full-wave models (MoM, FDTD etc.)
Accuracy of calculation depends on the
model used and on the exactness of
description of transmitting antennas
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Calculations
advantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Calculations
advantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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]
Vertical
cross-section,
azimuth 333°
Horizontal
cross-sections:
h=90 m
h=55 m
h=30 m
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Calculations
disadvantages
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
FEKO software
International
Telecommunication
Union
Comparison
measurement vs. calculation
Good agreement if properly done
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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 Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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 Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
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
International
ITU-T Technical Session on EMF
Geneva, 27 May 2009
Telecommunication
Union
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
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union
Thank you
Questions,
Comments?
ITU-T Technical Session on EMF
Geneva, 27 May 2009
International
Telecommunication
Union