IEC/IEEE 62704-1:2017

IEC/IEEE 62704-1 ®
Edition 1.0 2017-10
INTERNATIONAL
STANDARD
Determining the peak spatial-average specific absorption rate (SAR) in the
human body from wireless communications devices, 30 MHz to 6 GHz –
Part 1: General requirements for using the finite-difference time-domain (FDTD)
method for SAR calculations
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing being
secured. Requests for permission to reproduce should be addressed to either IEC at the address below or IEC’s

member National Committee in the country of the requester or from IEEE.

IEC Central Office Institute of Electrical and Electronics Engineers, Inc.
3, rue de Varembé 3 Park Avenue
CH-1211 Geneva 20 New York, NY 10016-5997
Switzerland United States of America
Tel.: +41 22 919 02 11 stds.ipr@ieee.org
Fax: +41 22 919 03 00 www.ieee.org
info@iec.ch
www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About the IEEE
IEEE is the world’s largest professional association dedicated to advancing technological innovation and excellence for
the benefit of humanity. IEEE and its members inspire a global community through its highly cited publications,
conferences, technology standards, and professional and educational activities.

About IEC/IEEE publications
The technical content of IEC/IEEE publications is kept under constant review by the IEC and IEEE. Please make sure
that you have the latest edition, a corrigendum or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets languages. Also known as the International
and iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, IEC publications issued since 2002. Some entries have
replaced and withdrawn publications. been collected from earlier publications of IEC TC 37, 77,

86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer
Service Centre: csc@iec.ch.
IEC/IEEE 62704-1 ®
Edition 1.0 2017-10
INTERNATIONAL
STANDARD
Determining the peak spatial-average specific absorption rate (SAR) in the

human body from wireless communications devices, 30 MHz to 6 GHz –

Part 1: General requirements for using the finite-difference time-domain (FDTD)

method for SAR calculations
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20; 33.060.20 ISBN 978-2-8322-4769-3

– 2 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Abbreviated terms . 15
5 Finite-difference time-domain method – basic definition . 16
6 SAR calculation and averaging . 17
6.1 Calculation of SAR in FDTD voxels . 17
6.2 SAR averaging . 18
6.2.1 General . 18
6.2.2 Calculation of the peak spatial-average SAR . 20
6.2.3 Calculation of the whole body average SAR . 24
6.2.4 Reporting peak spatial-average SAR and whole body average SAR. 24
6.2.5 Referencing peak spatial-average SAR and whole body average SAR . 24
6.3 Power scaling . 25
7 SAR simulation uncertainty . 26
7.1 Considerations for the uncertainty evaluation . 26
7.2 Uncertainty of the test setup with respect to simulation parameters . 27
7.2.1 General . 27
7.2.2 Positioning . 27
7.2.3 Mesh resolution . 28
7.2.4 Absorbing boundary conditions . 29
7.2.5 Power budget . 29
7.2.6 Convergence . 29
7.2.7 Dielectrics of the phantom or body model . 30
7.3 Uncertainty and validation of the developed numerical model of the DUT . 31
7.3.1 General . 31
7.3.2 Uncertainty of the DUT model (d ≥ λ/2 or d ≥ 200 mm) . 31
7.3.3 Uncertainty of the DUT model (d < λ/2 and d < 200 mm) . 33
7.3.4 Model validation . 34
7.4 Uncertainty budget . 35
8 Code verification. 36
8.1 General . 36
8.2 Code accuracy . 37
8.2.1 Free space characteristics . 37
8.2.2 Planar dielectric boundaries . 42
8.2.3 Absorbing boundary conditions . 45
8.2.4 SAR averaging . 48
8.3 Canonical benchmarks . 50
8.3.1 Generic dipole . 50
8.3.2 Microstrip terminated with ABC . 51
8.3.3 SAR calculation SAM phantom / generic phone . 52
8.3.4 Setup for system performance check . 53
Annex A (normative) Fundamentals of the FDTD method . 55
Annex B (normative) SAR Star . 59

© IEC/IEEE 2017
B.1 CAD files of the SAR Star . 59
B.2 Mesh lines for the SAR Star . 59
B.2.1 General . 59
B.2.2 Mesh lines for the homogeneous SAR Star . 59
B.2.3 Mesh lines for the inhomogeneous SAR Star . 60
B.3 Evaluation of the SAR Star benchmark . 60
B.3.1 General . 60
B.3.2 File format of the benchmark output. 60
B.3.3 Evaluation script . 61
Annex C (informative) Practical considerations for the application of FDTD . 65
C.1 Overview. 65
C.2 Practical considerations . 66
C.2.1 Computational requirements . 66
C.2.2 Voxel size . 67
C.2.3 Stability . 67
C.2.4 Absorbing boundaries . 67
C.2.5 Far-zone transformation . 68
C.3 Modelling requirements for sources and loads . 68
C.4 Calculation of S-parameters . 70
C.5 Calculation of power and efficiency . 70
C.6 Non-uniform meshes . 71
Annex D (informative) Background information on tissue modelling and anatomical
models . 73
D.1 Dielectric tissue properties . 73
D.2 Anatomical models of the human body . 73
D.3 Recommended numerical models of experimental phantoms . 73
D.3.1 Experimental head phantom . 73
D.3.2 Experimental body phantom. 74
Bibliography . 75

Figure 1 – Field components on voxel edges . 17
Figure 2 – Flow chart of the SAR averaging algorithm . 20
Figure 3 – Illustration of valid and used voxels in a valid averaging cube centred on the
highlighted voxel and an invalid averaging volume for which a new cube has to be
expanded about the surface voxel because it contains more than 10 % of background
material . 22
Figure 4 – Valid, used and partially used voxels . 23
Figure 5 – “Unused” location . 24
Figure 6 – Aligned parallel-plate waveguide and locations of the E -field components to
y
be recorded for TE-polarization . 37
Figure 7 – Permissible power reflection coefficient (grey range) for the aligned
absorbing boundary conditions . 46
Figure 8 – Tilted parallel-plate waveguide terminated with absorbing boundary
conditions and locations of the E -field components to be recorded for TE-polarization . 47
y
Figure 9 – Permissible power reflection coefficient (grey range) for the tilted absorbing
boundary conditions . 48
Figure 10 – Sketch of the testing geometry of the averaging algorithm . 49
Figure 11 – 3D view of the SAR Star . 50
Figure 12 – Geometry of the microstrip line . 52

– 4 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
Figure 13 – Geometry of the setup for the system performance check according to [31]. 53
Figure A.1 – Voxel showing the arrangement of the E- and H-field vector components
on a staggered mesh . 57
Figure A.2 – Voxels with different dielectric properties surrounding a mesh edge with
an E -component . 58
y
Figure C.1 – FDTD voltage source with source resistance . 69
Figure C.2 – Four magnetic field components surrounding the electric field component
where the source is located . 69

Table 1 – Voxel states during SAR averaging . 22
Table 2 – Factors contributing to the uncertainty of experimental and numerical SAR
evaluation . 27
Table 3 – Budget of the uncertainty contributions of the numerical algorithm and of the
rendering of the test- or simulation-setup . 30
Table 4 – Budget of the uncertainty of the developed model of the DUT. 34
Table 5 – Numerical uncertainty budget . 36
Table 6 – Results of the evaluation of the numerical dispersion characteristics . 42
Table 7 – Results of the evaluation of the numerical reflection coefficient . 44
Table 8 – Results of the dipole evaluation . 51
Table 9 – Results of the microstrip evaluation . 52
Table 10 – 1 g and 10 g psSAR for the SAM phantom exposed to the generic phone
for 1 W accepted antenna power as specified in [22]. 52
Table 11 – Dielectric parameters of the setup (Table 1 of [31]) . 54
Table 12 – Mechanical parameters of the setup (Tables 1 and 2 of [31]) . 54
Table 13 – psSAR normalized to 1 W forward power and feedpoint impedance (Tables
3 and 4 of [31]) . 54

© IEC/IEEE 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DETERMINING THE PEAK SPATIAL-AVERAGE SPECIFIC ABSORPTION
RATE (SAR) IN THE HUMAN BODY FROM WIRELESS
COMMUNICATIONS DEVICES, 30 MHz TO 6 GHz –

Part 1: General requirements for using the finite-difference
time-domain (FDTD) method for SAR calculations

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation.
IEEE Standards documents are developed within IEEE Societies and Standards Coordinating Committees of the
IEEE Standards Association (IEEE-SA) Standards Board. IEEE develops its standards through a consensus
development process, approved by the American National Standards Institute, which brings together volunteers
representing varied viewpoints and interests to achieve the final product. Volunteers are not necessarily
members of IEEE and serve without compensation. While IEEE administers the process and establishes rules
to promote fairness in the consensus development process, IEEE does not independently evaluate, test, or
verify the accuracy of any of the information contained in its standards. Use of IEEE Standards documents is
wholly voluntary. IEEE documents are made available for use subject to important notices and legal disclaimers
(see http://standards.ieee.org/IPR/disclaimers.html for more information).
IEC collaborates closely with IEEE in accordance with conditions determined by agreement between the two
organizations. This Dual Logo International Standard was jointly developed by the IEC and IEEE under the
terms of that agreement.
2) The formal decisions of IEC on technical matters express, as nearly as possible, an international consensus of
opinion on the relevant subjects since each technical committee has representation from all interested IEC
National Committees. The formal decisions of IEEE on technical matters, once consensus within IEEE Societies
and Standards Coordinating Committees has been reached, is determined by a balanced ballot of materially
interested parties who indicate interest in reviewing the proposed standard. Final approval of the IEEE
standards document is given by the IEEE Standards Association (IEEE-SA) Standards Board.
3) IEC/IEEE Publications have the form of recommendations for international use and are accepted by IEC
National Committees/IEEE Societies in that sense. While all reasonable efforts are made to ensure that the
technical content of IEC/IEEE Publications is accurate, IEC or IEEE cannot be held responsible for the way in
which they are used or for any misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
(including IEC/IEEE Publications) transparently to the maximum extent possible in their national and regional
publications. Any divergence between any IEC/IEEE Publication and the corresponding national or regional
publication shall be clearly indicated in the latter.
5) IEC and IEEE do not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC and IEEE are not responsible
for any services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or IEEE or their directors, employees, servants or agents including individual
experts and members of technical committees and IEC National Committees, or volunteers of IEEE Societies
and the Standards Coordinating Committees of the IEEE Standards Association (IEEE-SA) Standards Board,
for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect,
or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this
IEC/IEEE Publication or any other IEC or IEEE Publications.
8) Attention is drawn to the normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.

– 6 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
9) Attention is drawn to the possibility that implementation of this IEC/IEEE Publication may require use of
material covered by patent rights. By publication of this standard, no position is taken with respect to the
existence or validity of any patent rights in connection therewith. IEC or IEEE shall not be held responsible for
identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal
validity or scope of Patent Claims or determining whether any licensing terms or conditions provided in
connection with submission of a Letter of Assurance, if any, or in any licensing agreements are reasonable or
non-discriminatory. Users of this standard are expressly advised that determination of the validity of any patent
rights, and the risk of infringement of such rights, is entirely their own responsibility.
International Standard IEEE/IEC 62704-1 has been prepared by IEC technical committee 106:
Methods for the assessment of electric, magnetic and electromagnetic fields associated with
human exposure, in cooperation with the International Committee on Electromagnetic Safety
of the IEEE Standards Association , under the IEC/IEEE Dual Logo Agreement.
This publication is published as an IEC/IEEE Dual Logo standard.
This standard contains attached files in the form of CAD models and
reference results described in Annexes B and D. These files are available at:
http://www.iec.ch/dyn/www/f?p=103:227:0::::FSP_ORG_ID,FSP_LANG_ID:1303,25.
The text of this standard is based on the following IEC documents:
FDIS Report on voting
106/401A/FDIS 106/413/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
International Standards are drafted in accordance with the rules given in the ISO/IEC
Directives, Part 2.
A list of all parts in the IEC/IEEE 62704 series, published under the general title Determining
the peak spatial-average specific absorption rate (SAR) in the human body from wireless
communications devices, 30 MHz to 6 GHz, can be found on the IEC website.
The IEC technical committee and IEEE technical committee have decided that the contents of
this publication will remain unchanged until the stability date indicated on the IEC web site
under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
___________
1 A list of IEEE participants can be found at the following URL:
http://standards.ieee.org/downloads/62704/62704-1-2017/62704-1-2017_wg-participants.pdf.

© IEC/IEEE 2017
INTRODUCTION
Computational techniques have reached a level of maturity which allows their use in specific
absorption rate (SAR) assessment of wireless communication devices. Some wireless
communication devices are used in situations where experimental SAR assessment is
extremely complex or not possible at all. National regulatory bodies (e.g. US Federal
Communications Commission) encourage the development of consensus standards and
encouraged the establishment of the ICES Technical Committee 34 Subcommittee 2. The
benefits to the users and the regulators include standardized and accepted protocols,
anatomically correct body models, validation techniques, benchmark data, reporting format
and means for estimating the computational uncertainty in order to produce valid, accurate,
repeatable, and reproducible data.

– 8 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
DETERMINING THE PEAK SPATIAL-AVERAGE SPECIFIC ABSORPTION
RATE (SAR) IN THE HUMAN BODY FROM WIRELESS
COMMUNICATIONS DEVICES, 30 MHz TO 6 GHz –

Part 1: General requirements for using the finite-difference
time-domain (FDTD) method for SAR calculations

1 Scope
This part of IEC/IEEE 62704 defines the methodology for the application of the finite-
difference time domain (FDTD) technique when used for determining the peak spatial-average
specific absorption rate (SAR) in the human body exposed to wireless communication devices
with known uncertainty. It defines methods to validate the numerical model of the device
under test (DUT) and to assess its uncertainty when used in SAR simulations. Moreover, it
defines procedures to determine the peak spatial-average SAR in a cubical volume and to
validate the correct implementation of the FDTD simulation software. The applicable
frequency range is 30 MHz to 6 GHz.
NOTE Cubical averaging volumes are applied in all current experimental standards for the assessment of the
peak spatial-average SAR (psSAR) and recommended by [1], [2] and [3]. Other averaging volumes have been
proposed, for example, in [1], and may be included in future revisions of this document.
This document does not recommend specific SAR limits since these are found elsewhere, for
example, in the guidelines published by the International Commission on Non-Ionizing
Radiation Protection (ICNIRP) [1] or in IEEE Std C95.1 [3].
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
NOTE The experimental standards that define the SAM phantom and the testing positions are IEEE Std 1528 and
IEC 62209-1.
IEEE Std 1528, IEEE Recommended Practice for Determining the Peak Spatial-Average
Specific Absorption Rate (SAR) in the Human Head from Wireless Communications Devices:
Measurement Techniques
IEC 62209-1, Human Exposure to Radio Frequency Fields from Hand Held and Body Mounted
Wireless Communication Devices – Human Models, Instrumentation and Procedures – Part 1:
Procedure to determine the specific absorption rate (SAR) for devices used next to the ear
(frequency range of 300 MHz to 6 GHz)

IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV) (available at:
http://www.electropedia.org)
IEEE Standards Dictionary Online (subscription available at: http://dictionary.ieee.org)

© IEC/IEEE 2017
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the IEEE Standards
Dictionary Online, IEC 60050 (all parts) and the following apply.
ISO, IEC and IEEE maintain terminological databases for use in standardization at the
following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
• IEEE Dictionary Online: available at http://dictionary.ieee.org
3.1
excitation source
source with an associated signal which feeds electric or magnetic energy to one or more
edges of the mesh
Note 1 to entry: The amplitude of the signal is proportional to an arbitrary function of time.
3.1.1
added source
source whose amplitude is added to the present value of an E-field component on a mesh
edge at each time step of the FDTD algorithm
3.1.2
hard source
source whose amplitude replaces the present value of an E-field component on a mesh edge
at each time step of the FDTD algorithm
3.1.3
voltage source
source whose amplitude updates the present value of an E-field component on a mesh edge
at each time step of the FDTD algorithm considering the current through the mesh edge
represented by its surrounding H-fields and an internal resistance
3.2
antenna
part of a transmitting or receiving system that is designed to radiate or to receive
electromagnetic waves
3.3
feed-point
part of the radiating structure where the radio-frequency currents start to support
the electromagnetic fields that carry energy away from the antenna
Note 1 to entry: Often the feed-point of the antenna is not accessible because of mechanical support
requirements; in this case a connection point is available to inject radio-frequency energy into the antenna.
Normally, the connection point is a simple connector or a waveguide flange. If not collocated, the connection and
the feed-point of an antenna are interconnected by one or more sections of transmission line. By measuring the
antenna impedance at the connection point, if the electrical characteristics of the transmission lines between the
connection and the feed-point are known, it is possible to calculate the driving point or feed-point impedance of an
antenna.
3.4
antenna feed-point impedance
terminal or driving-point impedance
ratio of complex voltage to complex current at the terminals of a transmitting antenna, or the
ratio of the open-circuit voltage to the short-circuit current at the terminals of a receiving
antenna
– 10 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
3.5
attenuation
decrease in magnitude of a field quantity in the transmission from one point to another
Note 1 to entry: Attenuation is expressed as a ratio.
3.6
average power
P
time-averaged rate of energy transfer
t
P = P(t) dt (1)
∫
t – t
2 1
t
where P(t) is the instantaneous power
Note 1 to entry: The time duration could be source related (for example, the source repetition period, duty cycle)
or use related.
3.7
background material
material or tissue which is not considered for the averaging volume
Note 1 to entry: Most typically, a background material will be any lossless material, such as the free-space or air
surrounding the anatomical model. It also includes air enclosures or other lumina inside the body and tissues that
have been excluded from averaging, for example, by user selection.
3.8
benchmark simulation
simulation test specifically defined to validate simulation results based on comparison with a
reference
3.9
body
geometrical distribution of the dielectric properties and the mass densities of all live body
tissues including body fluids
Note 1 to entry: The contents of body lumina or foreign matter, such as medical implants or jewellery, are not
considered as part of the body.
3.10
conductivity
σ
ratio of the magnitude of the conduction-current density in a medium to the electric field
strength
Note 1 to entry: Conductivity is expressed in units of siemens per metre (S/m).
3.11
conservative estimate
estimate of the peak spatial-average SAR and whole-body average SAR as defined in this
document that is representative of what is expected to occur in the body of a significant
majority of population during normal operating conditions of wireless communication devices
Note 1 to entry: Conservative estimate does not mean the absolute maximum SAR value that could possibly occur
under every conceivable combination in the human body size, shape separation from the antenna and/or vehicle.

© IEC/IEEE 2017
3.12
coverage factor
k
factor that is used to obtain the expanded uncertainty from the combined uncertainty with a
known probability (P) of containing the true value of the measurand
Note 1 to entry: Specifically, k × (combined uncertainty) = (expanded uncertainty). When k = 1, P ≈ 0,68; k = 2,
P ≈ 0,95; k = 3, P ~ 0,999.
3.13
electric field
E-field
vector field of electric field strength
3.14
electric field strength
E
at a given point, the magnitude (modulus) of the vector limit of the quotient of the force that a
small stationary charge at that point will experience, by virtue of its charge, to the charge as
the charge approaches zero in a macroscopic sense
Note 1 to entry: This may be measured either in newtons per coulomb or in volts per metre. This term is
sometimes called the E-field intensity, but such use of the word intensity is deprecated, since intensity connotes
power in optics and radiation.
3.14.1
electric field strength
magnitude of the potential gradient in an E-field expressed in
units of potential difference per unit length in the direction of the gradient
3.14.2
electric field strength
magnitude of the E-field vector
Note 1 to entry: The electric field strength is expressed in volts per metre (V/m)
3.15
electrical length
length of a transmission medium or a transmission line, such as an antenna or a waveguide in
any medium including air
Note 1 to entry: Electrical length is expressed in wavelengths, radians, or degrees. When expressed in angular
units, it is a distance in wavelengths multiplied by 2π to yield radians, or by 360 to yield degrees.
3.16
electromagnetic field
EM field
electromagnetic phenomenon expressed in scalar or vector functions of space and time, for
example, a time-varying field associated with electric and magnetic forces and described by
Maxwell’s equations
3.17
far-field region
region of the field of an antenna where the angular field distribution is essentially,
independent of the distance from the antenna
Note 1 to entry: In this region (also called the free-space region), the field has predominantly plane wave
characteristics, i.e. the electric field strength and magnetic field strength distributions are locally uniform in planes
transverse to the direction of propagation.
Note 2 to entry: For larger antennas especially, the far-field region is also referred to as the Fraunhofer region.

– 12 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
3.18
incident wave
wave, travelling through a medium, in a specific direction, which impinges on a discontinuity
or a medium of different propagation characteristics
3.19
magnetic field
H-field
vector field of magnetic field strength
3.20
magnetic field strength
H
magnitude of the magnetic field vector
Note 1 to entry: The magnetic field strength is expressed in amperes per metre (A/m).
Note 2 to entry: For time harmonic fields in a medium with linear and isotropic magnetic properties, H is equal to
the ratio of the magnetic flux density B to the magnetic permeability of the medium µ, i.e., H = B/µ.
3.21
mesh
discrete representation of the simulation model as a set of voxels in a regular three-
dimensional Cartesian arrangement
Note 1 to entry: In the scientific literature, the mesh is often referred to as “grid”.
3.22
near-field region
region in the field of an antenna, located near the antenna, in which the electric and magnetic
fields do not have substantial plane-wave characteristics, but vary considerably from point to
point
Note 1 to entry: The term near-field region is often vaguely defined and has different meanings for large and
small antennas. The near-field region is further subdivided into the reactive near-field region, which is closest to
the antenna and contains most or nearly all of the stored energy associated with the field of the antenna, and the
radiating near-field region. If the antenna has a maximum overall dimension that is not large compared to the
wavelength, the radiating near-field region may not exist. For antennas large in terms of wavelength, the radiating
near-field region is sometimes referred to as the Fresnel region.
Note 2 to entry: For most antennas, the outer boundary of the reactive near-field region is commonly taken to
exist at a distance of λ/2π from the antenna surface.
3.23
perfect electric conductor
PEC
material with infinite electrical conductivity which does not dissipate any energy
3.24
relative permittivity
ε
r
ratio of the complex permittivity to the permittivity of free space
Note 1 to entry: The complex relative permittivity, ε = ε /ε , of an isotropic, linear, lossy dielectric medium is given
r o
 
σ ε ′′
r
 
by ε = ε ′ − jε ′′ = ε ′ − j = ε ′ 1− j = ε ′(1− j tanδ )
r r r r r r
 
′
ωε ε
0  r 
where
-12
ε is the free space permittivity (8,854 × 10 F/m);
ε ′ is the relative permittivity or dielectric constant;
r
σ is the conductivity in siemens per metre (S/m);
tanδ is the loss tangent.
© IEC/IEEE 2017
jωt
Note 2 to entry: For purposes of this document, the convention e is used to describe time-varying electric fields.
Note 3 to entry: The permittivity of biological tissues is frequency dependent and may be a complex tensor
quantity.
3.25
penetration depth
for a given frequency, the depth at which the electric field (E-field) strength of an incident
plane wave, penetrating into a lossy medium, is reduced to 1/e of its value just beneath the
surface of the lossy medium
Note 1 to entry: For a plane-wave incident normally on a planar half-space, the penetration depth δ is given in
Formula (2):
−
 
 
 
′   
1  µ ε ε σ
0 r 0
 
δ = 1+ −1 (2)
 
 
 
ω 2 ωε ′ε
 
 r 0 
 
 
 
3.26
permeability
µ
ratio of the magnetic flux density to the magnetic field strength at a point
Note 1 to entry: The permeability is expressed in units of henry per metre (H/m).
3.27
reactive field
electric and magnetic fields surrounding an antenna or other electromagnetic devices that
result in storage rather than propagation of electromagnetic energy
3.28
root-mean-square value
rms
positive square root of the mean value of the square of the function
taken over a given period
Note 1 to entry: For a periodic function y of t, the positive square root of y is
 1 
Y = y(t) dt (3)
rms
 
∫
T
 
where
Y is the rms value of y;
rms
t is any value of time;
T is the period.
3.29
root-sum-square value
rss
positive square root of the sum of the squares of the elements of a set of numbers
3.30
scattering
process that causes waves incident on discontinuities or boundaries of media to be changed
in direction, phase, or polarization

– 14 – IEC/IEEE 62704-1:2017
© IEC/IEEE 2017
3.31
specific absorption rate
SAR
time derivative (rate) of the incremental energy (dW) absorbed by (dissipated in) an
incremental mass (dm) contained in a volume element (dV) of a given density (ρ):
 
d  dW  d dW
SAR = =   (4)
 
 
dt dm dt ρ dV
 
 
Note 1 to entry: SAR is expressed in units of watts per kilogram (W/kg) or equivalently milliwatts per gram (mW/g).
Note 2 to entry: SAR can be related to the E-field at a point by
σ | E |
SAR =
2ρ
where
σ is the conductivity of the tissue in siemens per metre (S/m);
ρ is the mass density of the tissue in kilograms per cubic metre (kg/m );
E is the peak electric field vector in volts per metre (V/m).
Note 3 to entry: SAR can be related to the increase in temperature at a point by
c∆T
SAR ≈
∆t
t=0
where
∆T is the change in temperature in degree Celsius (ºC);
∆t is the duration of exposure in seconds (s);
c is the specific heat capacity in joules per kilogram and degree Celsius (J/kg ºC).
This assumes that measurements are made under “ideal” circumstances, i.e. no heat loss by thermal diffusion,
heat radiation, or thermoregulation (blood flow, sweating, etc.). Moreover, this expression is valid only in the initial,
linear regime of the temperature-time curve. If this linear regime does not exist, the provided expression is not
used.
3.31.1
peak spatial-average specific absorption rate
maximum average SAR within a local region based on a specific averaging volume or mass
Note 1 to entry: SAR is expressed in watts per kilogram (W/kg) or equivalently milliwatts per gram (mW/g).
Note 2 to entry: The specific averaging volume or mass can be, for example, any 1 g or 10 g of tissue in the
shape of a cube.
Note 3 to entry: For the purpose of this document, when the averaging mass is not specified the peak spatial-
average SAR refers to both 1 g and 10 g quantities. In several tables in this document, the peak spatial-average
SAR for 1 g and 10 g is simply denoted as 1 g and 10 g SAR.
3.31.2
spatial-average specific absorption rate
SAR within a local region based on a specific averaging volume or mass
Note 1 to entry: SAR is expressed in watts per kilogram (W/kg) or equivalently milliwatts per gram (mW/g).
Note 2 to entry: The specific averaging volume or mass can be, for example, any 1 g or 10 g of tissue in the
shape of a cube.
© IEC/IEEE 2017
3.32
whole body average specific absorption rate
quantity calculated as the power dissipated in the entire body divided by its mass
Note 1 to entry: SAR is expressed in watts per kilogram (W/kg) or equivalently milliwatts per gram (mW/g).
3.33
steady-state feed-point current
electric current flowing through the antenna feed-point in the steady-state regime of harmonic
excitation at the operating frequency
3.34
steady-state feed-point voltage
voltage established at the antenna feed-point in the steady-state regime of harmonic
excitation at the operating frequency
3.35
update coefficient
numerical value assigned to the voxel edges and faces calculated from the dielectric and
magnetic properties of the voxels that surround it
Note 1 to entry: The update coefficient is used to advance the numerical va
...