cotonou, benin, 19 july 2012 how sar may be used with base stations with some reference to iec 62232...

Cotonou, Benin, 19 July 2012

How SAR may be used with base stations with some reference to IEC

62232

Paolo Gemma,Senior Expert, Huawei

[email protected]

ITU Workshop on “Specific Absorption Rate (SAR) Measurement”

(Cotonou, Benin, 19 July 2012)

Summary

Regulatory aspect of SARMeasurement aspect

LaboratoryOn fieldSimulation

ITU recommendationsIEC Standards


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 equipmentThe 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


The ICNIRP limits of SAR


The ICNIRP reference values


SAR or reference Value?


SAR Measurement (1)

The SAR measurement from ICNIRP is the absolute measure of the effectSAR 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.


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 62209-1, IEC 62209-2, 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


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 testSimulation


ITU-T Technical Session on EMFGeneva, 27 May 2009

On field 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


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


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


ITU Recommendations on EMF

K.52 Guidance on complying with limits for human exposure to electromagnetic fieldsK.70 Mitigation techniques to limit human exposure to EMFs in the vicinity of radiocommunication stations.K.83 Monitoring of EMF levelsK.91 Guidance for assessment, evaluation and monitoring of human exposure to radio frequency electromagnetic fields

IEC 62232 (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;


IEC 62232 (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;


merci beaucoup pour merci beaucoup pour votre attentionvotre attention


cotonou, benin, 19 july 2012 how sar may be used with base stations with some reference to iec 62232...

Documents

account slide

effect sar measurement

sar measurement methodologies

band measurement slide

possible slide

sar measurements

sar value

sar verification