1. Paolo Gemma, Senior Expert, Huawei paolo.gemma@huawei.com
ITU Workshop on
“Specific Absorption Rate (SAR) Measurement” (Cotonou, Benin, 19 July 2012)
How SAR may be used with base stations with some reference to IEC 62232
Paolo Gemma,
Senior Expert, Huawei
Cotonou, Benin, 19 July 2012

2. Regulatory aspect of SAR Measurement aspect
Summary
Regulatory aspect of SAR
Measurement aspect
Laboratory
On field
Simulation
ITU recommendations
IEC Standards
Cotonou, Benin, 19 July 2012

3. Regulatory aspect of SAR
The SAR value are used for health regulatory aspect as protection of population health.
This is a factor normally linked to sites and not to equipment
The majority of countries use limits for SAR published by recognized International organization ICNIRP.
In some countries the SAR is used also for equipment regulatory aspect
Cotonou, Benin, 19 July 2012

4. The ICNIRP limits of SAR
Cotonou, Benin, 19 July 2012

5. The ICNIRP reference values
Cotonou, Benin, 19 July 2012

6. SAR or reference Value?
Cotonou, Benin, 19 July 2012

7. The SAR measurement from ICNIRP is the absolute measure of the effect
SAR measurement require the use of phantom to simulate the human body of part of the body.
For mobile communication frequency bands, SAR is usually the exposure metric to consider.
Cotonou, Benin, 19 July 2012

8. SAR Measurement (2)
Compliance assessments based on SAR are in general required for RF sources used close to the body (see EN 50383, IEC 62232, IEC , IEC , and EN 50413).
SAR measurements are mainly conducted by specialized laboratories, since the measurements are complex and require special equipment.
SAR measurement methodologies make use of phantoms simulating the human head or body which have been developed to provide conservative results with respect to exposure in real humans
Cotonou, Benin, 19 July 2012

9. Reference value verification
When the SAR verification is not possible due to the nature of the radio site.
Then normally the reference limits are used and conformance to these limits is verified with different methodologies
On field test
Simulation
Cotonou, Benin, 19 July 2012

10. On field 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)
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

11. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

12. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

13. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

14. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

15. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

16. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

17. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

18. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
FEKO software
ITU-T Technical Session on EMF
Geneva, 27 May 2009

19. Comparison measurement vs. calculation
Good agreement if properly done
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

20. 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
Details in paragraphs 2 to 6.
While some may think that the past is the past, wisdom is also what we learn from the past.
These paragraphs make interesting reading and should be kept in mind to avoid repeating the same mistakes
ITU-T Technical Session on EMF
Geneva, 27 May 2009

21. ITU Recommendations on EMF
K.52 Guidance on complying with limits for human exposure to electromagnetic fields
K.70 Mitigation techniques to limit human exposure to EMFs in the vicinity of radiocommunication stations.
K.83 Monitoring of EMF levels
K.91 Guidance for assessment, evaluation and monitoring of human exposure to radio frequency electromagnetic fields
Cotonou, Benin, 19 July 2012

22. IEC (1)
Determination of RF field strength and SAR in the vicinity of radiocommunication base stations for the purpose of evaluating human exposure.
Different methodologies considered:
RF field strength
SAR measurement
Computation methodologies
guidance on their applicability on
in situ evaluation of installed RBS
laboratory-based evaluations;
Cotonou, Benin, 19 July 2012

23. IEC (2)
1) product conformity: to establish that a RBS conforms to a defined set of limit conditions under its intended use;
2) compliance boundary: to establish the compliance boundary or boundaries for a RBS in relation to a defined set of limit conditions;
3) to evaluate RF field strength or SAR values at one or more evaluation locations, namely:
i) evaluation location(s) at arbitrary locations outside the control boundary to provide information for interested parties;
ii) evaluation location(s) at the control boundary to confirm validity of control boundary;
iii) evaluation location(s) within the control boundary with the specific conditions relevant to investigate an alleged over-exposure incident;
Cotonou, Benin, 19 July 2012

24. merci beaucoup pour votre attention
Cotonou, Benin, 19 July 2012