Title: Human Exposure to Electromagnetic Fields EMFs
1Human Exposure to Electromagnetic Fields (EMFs)
- Meeting ISO/IEC JTC1 SC31/WG4
-
- Jacques Hulshof
- NEDAP, Groenlo, The Netherlands
- Singapore, September 27-28, 2000
2ICNIRP ( International Commission on
Non-Ionizing Radiation Protection)Workshop of a
Concerted Action within the projectEnvironment
and Health - Health impact of Electromagnetic
FieldsHuman Exposure to Electromagnetic Fields
(EMFs) from several Radio Frequency
IDentification (RFID) Systems Jacques
HulshofNEDAP N.V., Groenlo, The
NetherlandsHelsinki, Finland, 19-22 September
2000(Revised on September 28, 2000 for ISO)
3Presentation contents
- Introduction Company profile
- RFID Frequency usage and fieldstrengths
Regulatory Issues regarding spectrum use. - RTTE Directive (1999/5/EC) and the prEN 50357
- Induced Current and SAR calculations on 4 major
RFID frequencies in use.
4Company profile
- N.V. Nederlandsche Apparatenfabriek NEDAP
- Five Divisions-EAS-RFID Acces Control
-Cattle Code Identification and -
management-Switched Mode Power Supplies-Special
Products - Job Radio Regulatory - and Safety issues
5Standardization Memberships
- ISO JTC 1/SC31/WG4 (SG3 and SG4)
- CENELEC TC 211 (WG 2)
- CEPT SE 24
- ETSI
- NEC 211(Dutch nat. Comm. of TC211)
- DKE 764 (German nat. Comm. of TC211)
- AIM (Automatic Identification Manufac.)
- US T6 (US Standardization Commission for RFID
and maybe in future EAS)
6Frequency Ranges and Applications
7International Communication Union (ITU)
- ITU Worldwide co-ordination in usage of
carrier frequencies - ITU devides the world in 3 regions
- -Region 1 Europe and Africa
- -Region 2 North and South America
- -Region 3 Far East, Asia and Australia
- Each country manages frequency allocations within
the ITU Guidelines
8Regulatory bodies and telecommunication standards
- EuropeRegulatory and Standardization Bodies
CEPT (Conférence Européene des Postes et
Télécommunication) ETSI (European
Telecommunication Standards Institute)Applicable
Regulations CEPT for the frequency planning - ERC REC 70-03
- ETSI for the the method of measurement
- (pr)EN 300 330 Frequency band 0.009- 25
MHz (pr)EN 300 220 Frequency band 25-1000
MHz - (pr)EN 300 440 Frequency band 1-25
GHz
9Other Regulatory bodies
- United States of America
- FCC (Federal Communication Committee) Regulati
on Part 15 of the FCC Rules - Canada DOC (Department of Communication) Regul
ation General Radio Regulations - Japan MPT (Ministery of Post and
Telecommunications) Regulation Japanese Radio
Law
10RFID for Item Management
RFID for Item Management
Target Frequencies
Target Frequencies
120,125,134 kHz
13.56 MHz
2.45
GHz
862-928 MHz
6.78 MHz
5.8
GHz
433 MHz
10 MHz
10 kHz
100 kHz
1 MHz
100 MHz
1
GHz
10
GHz
11RFID PrimerFrequencies
RFID Toll Roads Item Management
RFID Access Control Animal ID
RFID Item Management
RFID Smart Cards
Microwave EAS
Data Terminal
Cell Phone
Low Freq. EAS
Mid. Freq. EAS
TV
Data Modem
Radio Toys
Garage Door
AM
FM
CB
10 MHz
2.45 GHz
10 kHz
100 kHz
1 MHz
100 MHz
1000 MHz
300 GHz
12Frequency Bands and their Applications
13Several Kinds of Modulations
Baseline Sine Wave
Changing Phase
Changing Amplitude
Changing Frequency
FSK
PSK
ASK
14Applied frequencies below 135 KHz
- 120, 125, 132, 134.2 KHzFull duplex Transmitter
and Receiver on all the time - Half duplex or pulsed See drawing belowTrx on,
receiver off, activation of tag Trx off,
receiver on, reading tag
15Typical antenna sizes and fieldstrength at 120
KHz, at a distance of 20 cm. Basis is the 10 m
limit acc.to prEN 300 330
1613.56 MHz Signal 10 Modulation index
17Antenas sizes and fieldstrength at 20 cm on 13.56
and 6.78 MHz
18Regulations UHF Band
- USA and Canada 902-928 MHz, Peirp¹ 4 W
- Europe may assign the 862-870 MHz band for
frequency hopping systems request Peirp 4 W. - No allocation for UHF in Japan.
- UCC (United Code Council) and EAN (European
Article Numbering) started a project to have a
global harmonisation 862-928 MHz. - ¹Peirp Equivalent isotropic radiated power
19Regulations at 2.4 - 2.483 GHz
- USA has the band 2400-2483 MHz Peirp 4 W .
Canada has the same limits. - Europe may be changing 2446-2454 MHz -Peirp for
frequency hopping systems will possibly be
500 mW or 4 W -500 mW for Narrow band systems. - Japan 300 mW the band 2427-2471 MHz.
20Radio Regulatory Approval
- Type approval in every country
- RTTE¹ Directive 1999/5/EC in force per April 8th
2000 for CE and EFTA countries - Manufacturers Declaration
- CE Mark shows compliance
- No harmonised documents yet
- Transition period ¹RTTE stands for Radio and
telecommunication Terminal Equipment
21RTTE Council Directive 1999/5/CE
- Requirement for RFID DeviceArticle 3 (a) the
protection of the health and safety of the user
and any other persons. - To demonstrate compliance TC211 WG2 developed a
document prEN 50357.
22TC 211 WG2 prEN50357
- Procedure for evaluation of human exposure
electromagnetic Fields (EMFs) from Devices used
in Electronic Article Surveillance (EAS) Radio
Frequency Identification (RFID) and similar
equipment. - Values are taken from ICNIRP Guidelines and
Council Recommendation 1999/519/EC - This document is now in Public Enquiry
- Latest day by which this document has to be
announced at EC national level is 2001-10-01.
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26Guideline compliance with prEN 50357
- With the prEN 50357 one can also show
compliance to - ICNIRP Guidelines.
- RTTE Directive 1999/5/CE.
- Council Recommendation 1999/519/CE.
- Other national or international guidelines.
27Approach prEN 50357 3-Stage
- If system complies with a stage no requirement
for further assesment, otherwise go on to the
next stage. - Stage 1 Simple measurements against derived
reference levels. - Stage 2 More complex series of measurements,
coupled with modelling techniques to show
compliance with the Basic Restrictions - Stage 3 Detailled computer modelling and
analysis to show compliance with the basic
restrictions.
28 Stage 1
- Level 1 Simplified measurements at a distance of
20 cm from the antenna. In compliance with
Reference Levels no further measurements
necessary. - Level 2 Grid measurements.A grid is drawn
across the torso (see next two slides) and at
each point the fieldstrength is measured. The
average values should be calculated and compared
to the derived reference levels. In compliance
with reference levels no further measurements are
necessary.
29Vertical Wall or frame mounted Antenna
- Antenna Normative dimensions (in cm) Informative
dimensions (in cm) a/b/c X Z Height Width Depth
- Wall mounted unit 15 20 - 20-100 20-55 5
30Walk through Loop Antenna
- Antenna Normative dimensions (in cm) Informative
dimensions (in cm) a/b/c X Z Height Width Depth
- Walk-Through unit 15 20 85 200 100 5
31Stage 2 Analysis to show compliance to the basic
restrictions
- Case 1 Near field exposure in the band 100 KHz
to 30 MHz - For frequencies up to 100 KHz Induced current is
the dosimetric quantity. - For frequencies over 10 MHz SAR is the
dosimetric quantity. - Model used for below 100 KHz can be extended
above 100 KHz and below 30 MHz. - Frequencies between 100 KHz and 30 MHz both SAR
and Induced Current are the dosimetric
quantities.
32Relationship between Induced Current, SAR and H
in the band 0.1-30 MHz
- SAR J² / ? s and J s ? R B / 2
- s is electric tissue conductivity in S/m (See
Power Point 32 Conductivity as function of the
frequency) - ? is the density of tissue ( 1000 Kg/m³)
- J is the induced current density in (A/m²),
- ?2 p f in which f is the frequency (in Hz)
- B µ H, B is the magnetic flux density (in µT)
and H is the magnetic fieldstrength in A/m - The analysis presented is based on a conduction
path of radius R 0.2 m, appropriate for an
adult. This is still likely to be conservative - If the antenna is smaller than 40 cm R can be
reduced proportional.
33Conductivity in S/m as f (frequency)
34Prolate Spheroid Dimensions
- Note ICNIRP uses other dimensions for h and d,
but these are not applicable for RFID devices.
Scaling factors may be used
35Mean SAR in the band 0.1-30 MHz
- If mean SAR over the volume of tissue exposed in
the trunk is below 0.08 W/Kg, then the whole body
average will also be below the basic restriction. - This results in SAR s ? R² B² / 8 ?
- The relevant H - Field is given by H 23 /
f (f in MHz) - From 100 Khz to approx. 5-10 MHz one has still
to consider the induced current.
36Stage 2 Localised SAR for frequencies 30 MHz -
10 GHz
- Compliance with Basic Restrictions by means of
numerical modelling - ICNIRP Guidelines define localised SAR over 10
gr. of tissue - All transmitted power goes into 0.01 kg
- Basic restriction is 2 W/kg
- Any unit that supplies less than 20 mW
(10/10002000) from its antenna port will meet
the Basic Restriction. May be averaged over 6
min.
37Stage 3 Numerical modelling
- Computational dosimetry
- MRI data or photographs of anatomical sectional
diagrams - Include accurate tissue conductivities
- Reseach is continuing in this area New methods
and information will come available.
38Reference Level and Induced Current at 120 KHz
39Comparing measurements with the ICNIRP limits at
120 KHz
- Fieldstrenth at 20 cm distance of antenna 20 by
20 cm is 18.0 A/m Not in compliance with the
reference levels so calculation of induced
current J s p f R B - s 0.2 S/m f 0.12 MHz R 0.1 m and B
( in µT) 1.25 H (in A/m) - J 0.2 p 0.12 0.1 1.25 18.0 0.17
A/m² - Fieldstrenth at 20 cm distance of antenna 100 by
55 cm is 12.3 A/m Does not comply with the
reference level for the General Public so
calculating induced current (R 0.2 m) J
0.2 p 0.12 0.2 1.25 12.3 0.23 A/m² - Fieldstrength at 20cm of the antenna 1 by 2 m is
is 3.5 A/m. Complies with the reference levels.
No further modelling necessary.
40Compliance Table at 120 KHz
41Induced current and SAR limits at 6.78 MHz
42Comparing measurements with the ICNIRP limits at
6.78 MHz
- Fieldstrength at 20 cm distance of antenna 20 by
20 cm is 5.91 A/m Does not comply with the
reference levels so calculation of induced
current and SAR J s p f R B - s 0.5 S/m f 6.78 MHz R 0.1 m and
B ( in µT) 1.25 H (in A/m) - J 0.5 p 6.78 0.1 1.25 5.91 7.86
A/m² Localised SAR J²/?s 0.124 W/kg - Fieldstrength at 20 cm distance of antenna 100 by
55 cm is 0.73 A/m Does not comply with the
reference levels, so calculating induced current
and SAR (R 0.2 m) J 0.5 p 6.78 0.2
1.25 0.73 1.94 A/m² Whole body SAR limit is
H 23/f (f in MHz) 3.39 A/m - Fieldstrength at 20cm of the antenna 1 by 2 m is
0.14 A/m. Complies with reference levels. No
further modelling necessary.
43Compliance Table at 6.78 MHz
44SAR limits at 13.56 MHz
45Comparing measurements with the ICNIRP limits at
13.56 MHz
- Fieldstrength at 20 cm distance of antenna 20 by
20 cm is 2.7 A/m Does not comply with the
reference levels so calculation of SAR J s
p f R B - s 0.5 S/m f 13.78 MHz R 0.1 m and
B ( in µT) 1.25 H (in A/m) - J 0.5 p 13.56 0.1 1.25 2.7 7.19
A/m² Localised SAR J²/?s 0.103 W/kg - Fieldstrength at 20 cm distance of antenna 100 by
55 cm is 0.73 A/m Does not comply with the
reference levels, so calculating SAR (R 0.2
m) Whole body SAR H limit is H 23/f (f in
MHz) 1.70 A/m - Fieldstrength at 20cm of the antenna 1 by 2 m is
is 0.064 A/m. Complies with the reference levels.
No further modelling necessary.
46Compliance Table at 13.56 MHz
47(1) SAR measurement and calculations at 900 MHz
and 2.45 GHz
- For 900 MHz and 2.4 GHz same modelling and -
basic restrictions can be applied, because the
SAR is independent of the frequency. - The allowed Peirp is 4 W. With an antenna gain of
approx. 8 dB, this comes down to a power at the
antenna port of 600 mW, which is far above the
mentioned 20 mW. - So we have to perform modelling.
- Because the antennas are rather small the
approach is localised SAR 2 W/kg, to be
averaged over any 10 gr. of tissue. This results
in 20 mW in 10 gr. of tissue. - Tissue density is 1000 kg/m³. Assuming 10 gr is a
cubic with sides 2.16 cm.
48(2) SAR measurements and calculations at 900 MHz
and 2.45 GHz
- The surface results in 2.16 2.16 4.66 cm²
- Absorbed power in 10 gr of tissue is 4.66
10-4 Pd. In which Pd in W/m ² is Power
density at a distance d 20 cm. - Allowed absorbed power is 20 mW, so 4.66 10 -4
Pd 20 10-3 Pd 42.9 W/m² - This comes down to an allowed Peirp Pd 4 p
d² 21.6 W which may be averaged over a 6 min
period. - So the 4 W is far below the limit.
49Modelling Results for a 60 cm by 30 cm Prolate
Spheroid
Magnetic Field
50CONCLUSIONS
- It is shown in this presentation that Radio
Frequency IDentification Systems and its
frequencies equipped with typical antennas are in
compliance with the reference levels and/or the
basic restrictions from ICNIRP. The systems also
comply with the prEN 50357, the Council
Recommendation 1999/519/EC and the RTTE
Directive 1999/5/EC. Of course always
measurements have to be performed on actual
systems according to the prEN 50357.
51Literature References
- Guidelines for limiting exposure to time-varying
electric, magnetic, and electromagnetic fields
(up to 300 GHz) by the International Commission
on Non-Ionising Radiation Protection (ICNIRP),
Health Physics, Volume 74, Number 4, pp 494-522,
April 1998. - The limitation of exposure of the general public
to electromagnetic fields 0-300 GHz, European
Council Recommendation 1999/519/EC, Official
Journal of the European Communities, L199, p59,
1999. - The harmonisation of the laws of member states
relating to electrical equipment designed for use
within certain voltage limits, European Council
Directive 73/23/EEC, Official Journal of the
European Communities, L77, p29, 1973. - Radio equipment and telecommunications terminal
equipment and the mutual recognition of their
conformity, European Council Directive
1999/5/EC, Official Journal of the European
Communities, L91, p10, 1999. - Occupational exposure to electromagnetic fields
practical application of NRPB guidance, P.J.
Chadwick, NRPB-R301, National Radiological
Protection Board, Chilton, Didcot, Oxfordshire,
UK, 1998. - System model for Inductive ID systems, by K.
Fockens for ISO JTC 31/WG 4/SG3, March 2000. - Procedures for the evaluation of Human Exposure
to electromagnetc fields (EMFs) from Devices
used in Electronic Article Surveillance (EAS),
radio frequency (RFID) and similar Applications,
Cenelec prEN 50357.