IEC/IEEE 62704-3:2017

IEC/IEEE 62704-3 ®
Edition 1.0 2017-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Determining the peak spatial-average specific absorption rate (SAR) in the
human body from wireless communications devices, 30 MHz to 6 GHz –
Part 3: Specific requirements for using the finite difference time domain (FDTD)
method for SAR calculations of mobile phones

Détermination du débit d'absorption spécifique (DAS) maximal moyenné dans
le corps humain, produit par les dispositifs de communication sans fil, 30 MHz
à 6 GHz –
Partie 3: Exigences spécifiques pour l'utilisation de la méthode des différences
finies dans le domaine temporel (FDTD) pour les calculs de DAS des téléphones
mobiles
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IEC/IEEE 62704-3 ®
Edition 1.0 2017-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Determining the peak spatial-average specific absorption rate (SAR) in the

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

Part 3: Specific requirements for using the finite difference time domain (FDTD)

method for SAR calculations of mobile phones

Détermination du débit d'absorption spécifique (DAS) maximal moyenné dans

le corps humain, produit par les dispositifs de communication sans fil, 30 MHz

à 6 GHz –
Partie 3: Exigences spécifiques pour l'utilisation de la méthode des différences

finies dans le domaine temporel (FDTD) pour les calculs de DAS des téléphones

mobiles
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20 ISBN 978-2-8322-4772-3

– 2 – IEC/IEEE 62704-3:2017
© IEC/IEEE 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Abbreviated terms . 9
5 Simulation procedure . 10
5.1 General . 10
5.2 General considerations . 10
5.3 General mesh settings . 10
5.4 Simulation parameters . 10
5.5 DUT model . 10
5.5.1 General . 10
5.5.2 Antenna . 12
5.5.3 RF source . 12
5.5.4 PCB . 13
5.5.5 Screen . 13
5.5.6 Battery and other larger metallic components . 14
5.5.7 Casing . 14
5.6 SAR calculation using phantom models. 14
5.6.1 General . 14
5.6.2 Head phantom model . 15
5.6.3 Body phantom model . 18
5.6.4 Phantom mesh generation . 18
5.7 Recording of results . 18
5.8 Peak spatial-average SAR calculation . 19
6 Benchmark models . 19
6.1 General . 19
6.2 Generic metallic box phone for 835 MHz and 1 900 MHz . 19
6.3 GSM/UMTS mobile phone . 21
6.4 Generic multi-band patch antenna mobile phone . 22
6.5 Neo Free Runner mobile phone . 24
7 Computational uncertainty . 25
7.1 General considerations . 25
7.2 Uncertainty of the test setup with respect to simulation parameters . 26
7.3 Uncertainty of the developed numerical model of the DUT . 26
7.4 Validation of the developed numerical model of the DUT. 26
7.5 Uncertainty budget . 26
8 Reporting simulation results . 27
8.1 General considerations . 27
8.2 DUT . 27
8.3 Simulated configurations . 27
8.4 Numerical simulation tool . 28
8.5 Results of the benchmark models . 28
8.6 Uncertainties. 28
8.7 SAR results . 28

© IEC/IEEE 2017
Annex A (informative) Additional results for the generic mobile phone with integrated
multiband antenna . 29
Annex B (informative) Additional results for the Neo Free Runner mobile phone . 31
Bibliography . 35

Figure 1 – An example of a multi-band antenna consisting of two metallic elements for
the GSM and UMTS frequency bands . 12
Figure 2 – An example of a source gap position that is inserted in replacement of a
real-life feeding spring pin. 13
Figure 3 – An example of a microstrip feed line. 13
Figure 4 – Orientation of the mobile phone model prior to positioning against the head
or the body phantom . 15
Figure 5 – Orientation of the SAM phantom prior to positioning against the DUT shown
in Figure 4 . 16
Figure 6 – Suggested steps for the cheek position of the DUT against the SAM
phantom . 16
Figure 7 – Tilt position of the DUT against the SAM phantom . 17
Figure 8 – Example of the full model space that includes the DUT and the SAM
phantom for the numerical simulations for the right cheek position . 17
Figure 9 – Example of the model space for the DUT/body phantom calculation setup . 18
Figure 10 – The SAM head phantom and the generic metallic box phone . 19
Figure 11 – Physical dimensions of the generic metallic box phone . 20
Figure 12 – Generic GSM/UMTS mobile phone . 21
Figure 13 – Generic mobile phone with integrated multiband patch antenna . 23
Figure 14 – CAD model of the Neo Free Runner mobile phone . 24
Figure A.1 – Real part of the input impedance of the antenna obtained with three
different commercially available software products. 29
Figure A.2 – Imaginary part of the input impedance of the antenna obtained with three
different commercially available software products. 30
Figure B.1 – Basic version of the Neo Free Runner CAD model . 31
Figure B.2 – Intermediate version of the Neo Free Runner CAD model . 31
Figure B.3 – Full version of the Neo Free Runner CAD model . 32
Figure B.4 – Interlaboratory comparison results of the free space reflection coefficient
for the basic CAD model . 32
Figure B.5 – Interlaboratory comparison results of the free space reflection coefficient
for the intermediate CAD model . 33
Figure B.6 – Interlaboratory comparison results of the free space reflection coefficient
for the full CAD model . 33

Table 1 – Dielectric parameters of the materials of the generic phone. 20
Table 2 – Peak spatial-average SAR for 1 g and 10 g of the benchmark . 21
Table 3 – Dielectric properties of the materials of the generic GSM/UMTS mobile
phone . 22
Table 4 – Peak 1 g and 10 g SAR results of the GSM/UMTS mobile phone . 22
Table 5 – Limits of the output parameters for the generic multi-band mobile phone . 23
Table 6 – Peak 1 g and 10 g SAR results of the GSM/UMTS mobile phone . 24
Table 7 – Dielectric properties of the materials of the Neo Free Runner mobile phone . 25

– 4 – IEC/IEEE 62704-3:2017
© IEC/IEEE 2017
Table 8 – Peak 1 g and 10 g SAR results of the Neo Free Runner mobile phone . 25
Table 9 – Overall uncertainty budget . 27
Table B.1 – Frequency limits of the −6 dB reflection coefficient for the three different
versions of the Neo Free Runner mobile phone . 34

© 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 3: Specific requirements for using the finite difference time domain
(FDTD) method for SAR calculations of mobile phones

FOREWORD
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© IEC/IEEE 2017
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International Standard IEC/IEEE 62704-3 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 International Committee on Electromagnetic Safety of
the IEEE Standards Association , under the IEC/IEEE Dual Logo Agreement between IEC and
IEEE.
This publication is published as an IEC/IEEE Dual Logo standard.
The text of this standard is based on the following IEC documents:
FDIS Report on voting
106/404/FDIS 106/414/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.
This standard contains attached files in the form of CAD models described in Clause 6. These
files are available at:
http://www.iec.ch/dyn/www/f?p=103:227:0::::FSP_ORG_ID,FSP_LANG_ID:1303,25
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
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A list of IEEE participants can be found at the following URL:
http://standards.ieee.org/downloads/62704/62704-3-2017/62704-3-2017_wg-participants.pdf.

© IEC/IEEE 2017
INTRODUCTION
The increasing complexity of assessing product compliance with exposure standards
according to specific absorption rate (SAR) limits calls for new compliance or pre-compliance
techniques. Currently standardized experimental SAR compliance assessments of wireless
communication devices are time-consuming and costly. Computational techniques have
reached a level of maturity which allows their use in the pre-compliance assessments of
wireless communication devices such as mobile phones. For example, pre-compliance testing
is important for mobile phone manufacturers in their product development phase where this
document may be applied. The benefits to the users and manufacturers include standardized
and accepted protocols, validation techniques, benchmark results, reporting format and
means for estimating the overall uncertainty in order to produce valid, repeatable, and
reproducible data.
The results obtained by following the protocols specified in this document represent a
conservative estimate of the peak spatial-average SAR induced in the standard human body
models due to mobile phones. The protocols set forth herein produce results subject to
modelling, simulations and other uncertainties that are defined in this document.
It is not the intent of this document to provide a result representative of the absolute
maximum SAR value possible under every conceivable combination of human body and
mobile phone usage. The following items are described in detail: simulation concepts,
simulation techniques, finite difference time domain (FDTD) numerical method, benchmark
results, standardized numerical models of the human body. Procedures for validating the
numerical tools used for SAR simulations and assessing the SAR simulation uncertainties are
provided. This document is intended primarily for use by engineers and other specialists who
are familiar with electromagnetic (EM) theory, numerical methods, and, in particular, FDTD
techniques. This document does not recommend specific SAR limit values since these are
found in other documents.
– 8 – IEC/IEEE 62704-3:2017
© 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 3: Specific requirements for using the finite difference time
domain (FDTD) method for SAR calculations of mobile phones

1 Scope
This part of IEC/IEEE 62704 defines the concepts, techniques, benchmark phone models,
validation procedures, uncertainties and limitations of the finite difference time domain
(FDTD) technique when used for determining the peak spatial-average specific absorption
rate (SAR) in standardized head and body phantoms exposed to the electromagnetic fields
generated by wireless communication devices, in particular pre-compliance assessment of
mobile phones, in the frequency range from 30 MHz to 6 GHz. It recommends and provides
guidance on the numerical modelling of mobile phones and benchmark results to verify the
general approach for the numerical simulations of such devices. It defines acceptable
modelling requirements, guidance on meshing and test positions of the mobile phone and the
phantom models. This document does not recommend specific SAR limits since these are
found in other documents, e.g. IEEE C95.1-2005[1] and ICNIRP[2].
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.
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV) (available at:
www.electropedia.org)
IEC 62209-1, Measurement procedure for the assessment of specific absorption rate of
human exposure to radio frequency fields from hand-held and body-mounted wireless
communication devices – Part 1: Devices used next to the ear (Frequency range of 300 MHz
to 6 GHz)
IEC 62209-2, Human exposure to radio frequency fields from hand-held and body-mounted
wireless communication devices – Human models, instrumentation, and procedures – Part 2:
Procedure to determine the specific absorption rate (SAR) for wireless communication
devices used in close proximity to the human body (frequency range of 30 MHz to 6 GHz)
IEC/IEEE 62704-1:2017, 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
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
IEEE Standards Dictionary Online
___________
Numbers in square brackets refer to the Bibliography.
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 IEC/IEEE 62704-1, 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
cell
discretization step along a given axis of the Cartesian coordinates
3.2
component
part present in the mobile phone
EXAMPLE Antenna, battery, etc.
3.3
handset
hand-held device intended to be operated close to the body, consisting of an acoustic output
or earphone and a microphone, and containing a radio transmitter and a receiver
3.4
object
solid identified by computer-aided design (CAD) criteria
4 Abbreviated terms
ACIS 3-D file format derived from its authors’ names (Alan Charles, Ian’s System)
CAD computer-aided design; commonly used file formats are IGES, DXF and SAT
DCS digital communication system
DUT device under test
DXF digital exchange file
ERP ear reference point
FDTD finite difference time domain
GSM global system for mobile communication
IGES international graphics exchange standard
LCD liquid crystal display
PCB printed circuit board
PEC perfect electric conductor
PML perfectly matched layers
RF radio frequency
SAM specific anthropomorphic mannequin
SAR specific absorption rate
SAT standard ACIS text
UMTS universal mobile telecommunication system

– 10 – IEC/IEEE 62704-3:2017
© IEC/IEEE 2017
5 Simulation procedure
5.1 General
Clause 5 presents the steps that shall be followed to compute SAR from a mobile phone
placed against a head or a body phantom. The procedure requires voxel models derived from
the CAD data files of the DUT and of either the SAM head phantom or the body phantom.
5.2 General considerations
The practical considerations for the application of the FDTD method are provided in Annex C
of IEC/IEEE 62704-1:2017. Since the standard FDTD method relies on the Cartesian Yee cell,
stair casing of curved surfaces is a problem that needs special consideration, particularly for
the case of the DUT and the SAM head phantom. To limit stair casing, the positioning of the
DUT against the SAM phantom shall be achieved by performing transformations such as
translations and rotations on the SAM phantom only. The body phantom should preferably be
reconstructed using the built-in drawing features of the numerical simulation tool when
available. It can be easily aligned with both the handset and the FDTD axes.
5.3 General mesh settings
For the FDTD method, the intrinsic problem of choosing a sufficiently small cell or grid size
yet limit the memory requirements can be challenging. The wavelength in the material with the
highest relative permittivity generally dictates the required minimum grid step. To mesh the
free-space surrounding the phone and the phantom, a cell size corresponding to about λ/30 to
λ/10 may be sufficient, where λ is the smallest wavelength corresponding to the wave
propagation in the material with the highest relative permittivity. Since the relative
permittivities of the materials present in a mobile phone are usually low – typically in the
range 2 to 10 – the tissue equivalent liquid is expected to have the highest relative
permittivity. Since this is generally insufficient for modelling the smaller components in a
mobile phone, it may be necessary to further decrease the cell size to fully account for fine
details such as slots or gaps or small components. The cell size may then be much smaller
than the minimum cell size imposed by the highest relative permittivity of the materials
present in the computational domain.
5.4 Simulation parameters
Practical considerations for the application of the FDTD such as voxel size, stability,

absorbing boundaries are described in IEC/IEEE 62704-1:2017, Annex C.
5.5 DUT model
5.5.1 General
Prior to performing the SAR calculation using the head or the body phantom, the numerical
simulation shall first be undertaken considering the DUT alone, i.e. free space configuration.
The validity of the numerical model of the DUT shall be verified as described in Clause 7.
A DUT model normally contains many different solids, typically more than one hundred,
making this model a very complex structure to handle. Given the complexity of recent
generation wireless handsets used by consumers and the extensive time required for device
modelling, the only practical approach for producing the FDTD mesh is by importing the
mechanical CAD file of the DUT, and to automatically generate the FDTD model for the
handset. The file with the model shall be exported from the mechanical engineering CAD tool
in a format that can be easily imported into the FDTD simulation tool (usually SAT or IGES file
format). Prior to the export of the CAD model, all parts shall be assembled and correctly
aligned with respect to each other.
When the mechanical CAD file is not available, it may be acceptable to reconstruct the
numerical model based on information such as the geometrical dimensions and positions of

© IEC/IEEE 2017
the different components of the DUT [3]. In this document, the numerical model of the DUT is
considered as a CAD model whether it is obtained following a numerical reconstruction or
available as an export of a mechanical CAD file. The validity of the numerical model shall be
demonstrated according to 7.4.
It is most important that the components present in the DUT model are assigned the correct
material dielectric parameters. After import of the CAD file into the FDTD simulation tool, the
correct material shall be assigned to each object to be meshed. The components and
dielectric properties should be verified by a CAD engineer familiar with the physical and
mechanical construction of the mobile phone.
Prior to meshing, the cell size requirements shall be established. This can be done in several
ways, including automatic mesh generation, by a CAD object or group of objects, or manually.
In order to provide an accurate mesh that will require minimal computer memory and run
times, it is common practice to use a graded mesh, also called non-uniform mesh [4]. A
graded mesh allows the FDTD mesh cell sizes to vary with position in one dimension. This
approach allows smaller cells to be used where needed in order to accurately describe small
but important CAD objects. A typical application for smaller mesh cells is in the antenna
region which usually consists of slots.
While the above basic approach is a good start, there are exceptions that shall be considered.
For example, the CAD objects may not have continuous surfaces. This can happen when the
surface of the object is formed by the combination of separate facets and these facets may
not join precisely at their intersections, leaving unintended gaps. This problem can be
mitigated by "healing" the object manually to close the gaps (the healing feature is usually
available in most commercially available FDTD simulation tools to fix connection problems
among CAD objects to be fixed). However, for CAD objects with large gaps it may be
impossible to develop an accurate FDTD mesh without manual intervention.
It is recommended that the larger metallic components or parts should be made into separate
objects for which specific grid settings can be applied. In particular, the antenna model shall
be a separate object so that this structure can be meshed as accurately as possible. The
metallic parts of the model shall be aligned and connected so that artificial floating of
electrically connected objects does not occur. Usually the printed circuit board (PCB) is not
well represented in the CAD model. It is typically modelled as a few thin metallic layers
interleaved with dielectric material [5]. However, it is acceptable to model the PCB as one
thick solid metallic object. It is important to note that if the PCB is not correctly modelled, it
will be seen as an invalid CAD model according to 7.4.
In order to optimize the computational resources, the components in the DUT model, for
instance components located inside shielded cans, that are not expected to have noticeable
impact to SAR distributions may be removed [6]. Consequently, such metallic components
shall be given meshing priority over a component of lesser impact on SAR distribution.
Components with the same material dielectric property that are in physical contact shall be
united to form one solid. As a minimum requirement, essential parts such as antenna,
chassis, PCB, display or screen, battery, other relatively large metallic components and the
dielectric material supporting the antenna shall be modelled accurately. The meshing order of
the objects or groups of objects shall be specified so that objects that touch, or perhaps even
overlap, are correctly represented in the FDTD model.
Once the meshing has been completed, the resulting FDTD model of the handset shall be
viewed and verified for accuracy. Critical areas such as the antenna region and other
conductive components shall be carefully examined since the most important objects of the
DUT model are the metallic components because they have the biggest impact on the SAR
distribution.
As a guideline for the mesh generation, the components of the mobile phone that are
expected to have the relatively highest impact on the SAR distribution are provided in 5.5.2 to
5.5.7.
– 12 – IEC/IEEE 62704-3:2017
© IEC/IEEE 2017
5.5.2 Antenna
The antenna of the DUT is the most important component to be modelled and the grid step
shall be chosen so as to resolve all details such as slots and gaps contained in it. Figure 1
shows the typical appearance of a top-mounted multi-band patch antenna for the GSM and
UMTS frequency bands of operation.
x
z
IEC
NOTE The two separate metallic elements constituting the antenna are highlighted.
Figure 1 – An example of a multi-band antenna consisting of two metallic
elements for the GSM and UMTS frequency bands
The shape of this particular antenna is rather complex and the cell size shall be chosen such
that all details are resolved. In particular, if the antenna consists of separate metallic
elements, most often used for operations at higher and/or multiple frequency bands, it is
important to use a cell size that is less than half the separation between the elements. In the
example shown in Figure 1, a cell size of 0,25 mm or less is necessary along the z-axis
because the gap between the left and the middle branches of the antenna is only 0,5 mm. In
the actual meshing, at least three cells are required to model the separations; otherwise, the
tangential field in the gap to the parasitic element will not be simulated correctly. Furthermore,
to correctly model the slot on the right metallic element of this antenna, a similar cell size is
required along the x-axis.
5.5.3 RF source
The antenna feed model shall be constructed according to the feed used in the actual device.
Usually a coaxial feed is connected to a feeding pin, in which case a classic FDTD feed gap
source model shall be used. The actual feeding pin shall be replaced with the FDTD source
excitation gap, as shown in Figure 2, and there shall be a gap of at least one cell
corresponding to the actual gap dimension in the DUT model.
When the antenna is fed by a different means (e.g. a microstrip line as shown in Figure 3), the
excitation source shall be modelled accordingly so that it is representative of the feed.

© IEC/IEEE 2017
IEC
Figure 2 – An example of a source gap position that is inserted in
replacement of a real-life feeding spring pin
IEC
Figure 3 – An example of a microstrip feed line
5.5.4 PCB
The PCB is a sandwich structure that typically consists of several metallic sheets interleaved
with dielectric layers. Modelling the PCB as a sandwiched structure has been found to be
important in order to compute the losses in the PCB properly [5], but it requires a very fine
cell size, usually 0,1 mm or less. Furthermore, it is usually difficult to model the
interconnections between the different layers of the PCB. To alleviate this difficulty, the PCB
should rather be modelled as a metallic solid since doing so is very unlikely to lead to under-
estimation of the SAR.
5.5.5 Screen
The screen normally consists of several glass layers that may be merged into one solid object
for simplicity, in which case an effective relative permittivity, typically an average of the
different dielectric properties of the different materials, shall be used. If the screen contains
metallic parts or conductive components, those parts shall be modelled as separate objects
embedded in the display. For example, a metallic frame is sometimes placed around the screen.
The screen display is attached to the PCB at several points and there is sometimes a narrow
gap between them. The cell size shall be small enough to resolve this gap properly and it can
be necessary to increase the resolution around the screen to resolve the air gaps around it.
This is important since high surface currents will flow on the metallic parts. If the screen is not
correctly and properly connected to the PCB, a completely different SAR distribution may
result.
– 14 – IEC/IEEE 62704-3:2017
© IEC/IEEE 2017
5.5.6 Battery and other larger metallic components
The outer surface of the battery pack is typically covered with a thin metallic foil, which
enables the battery to be treated as a solid metallic object.
Other metallic components in the phone include camera housing, vibrator rotor, external
antenna connector, etc. The cells representing these components shall be examined carefully
before the FDTD simulation can be started. It is important to investigate the final grid for
artificial gaps between larger metallic components. When objects in the CAD model are not
perfectly aligned, sub-millimetre gaps can introduce artificial breaks or discontinuity and lead
to computational errors. In such situations, it is necessary to manually adjust such objects or
replace the components with a metallic structure of the same outer dimensions. Also, thin
metallization on the DUT front-side or inside the DUT shall be checked for artificial gaps in the
CAD and FDTD models. This is also important for flex films that run between components, for
instance bet
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