Human Exposure to Electromagnetic Fields EMFs

1
Human Exposure to Electromagnetic Fields (EMFs)

• Meeting ISO/IEC JTC1 SC31/WG4
• Jacques Hulshof
• NEDAP, Groenlo, The Netherlands
• Singapore, September 27-28, 2000

2
ICNIRP ( 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)
3
Presentation 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.

4
Company 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

5
Standardization 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)

6
Frequency Ranges and Applications
7
International 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

8
Regulatory 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

9
Other 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

10
RFID 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
11
RFID 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
12
Frequency Bands and their Applications
13
Several Kinds of Modulations
Baseline Sine Wave
Changing Phase
Changing Amplitude
Changing Frequency
FSK
PSK
ASK
14
Applied 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

15
Typical antenna sizes and fieldstrength at 120
KHz, at a distance of 20 cm. Basis is the 10 m
limit acc.to prEN 300 330
16
13.56 MHz Signal 10 Modulation index
17
Antenas sizes and fieldstrength at 20 cm on 13.56
and 6.78 MHz
18
Regulations 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

19
Regulations 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.

20
Radio 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

21
RTTE 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.

22
TC 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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Guideline 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.

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Approach 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.

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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.

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Vertical 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

30
Walk 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

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Stage 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.

32
Relationship 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.

33
Conductivity in S/m as f (frequency)
34
Prolate Spheroid Dimensions

• Note ICNIRP uses other dimensions for h and d,
  but these are not applicable for RFID devices.
  Scaling factors may be used

35
Mean 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.

36
Stage 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.

37
Stage 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.

38
Reference Level and Induced Current at 120 KHz
39
Comparing 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.

40
Compliance Table at 120 KHz
41
Induced current and SAR limits at 6.78 MHz
42
Comparing 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.

43
Compliance Table at 6.78 MHz
44
SAR limits at 13.56 MHz
45
Comparing 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.

46
Compliance 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.

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(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.

49
Modelling Results for a 60 cm by 30 cm Prolate
Spheroid
Magnetic Field
50
CONCLUSIONS

• 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.

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Literature 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.