1 Name
of Standard [see Note
1]
This Standard is the Radiocommunications
(Electromagnetic Radiation — Human Exposure) Standard 2003.
2 Commencement
This Standard commences on 1 March 2003.
3 Revocation
The Radiocommunications (Electromagnetic
Radiation — Human Exposure) Standard 2001 is revoked.
4 Object
of Standard
This Standard regulates the performance of
particular radiocommunications transmitters, to protect the health and safety
of persons exposed to electromagnetic radiation from the transmitters.
5 Definitions
(1) In this Standard:
Act means the Radiocommunications Act 1992.
ARPANSA Standard means
the Radiation Protection Standard for Maximum Exposure Levels to
Radiofrequency Fields – 3 kHz to 300 GHz published by
the Australian Radiation Protection and Nuclear Safety Agency and assigned the
number ISBN 0‑0642‑79400‑6.
Note The ARPANSA Standard may be obtained
from the Australian Radiation Protection and Nuclear Safety Agency website
http://www.arpansa.gov.au .
AS 2772.2 means the Australian
Standard Radiofrequency radiation Part 2: Principles and methods
of measurement – 300 kHz to 100 GHz (AS 2772.2)
published by Standards Australia.
aware user device means a hand‑held or
body‑worn radiocommunications transmitter that operates on a push‑to‑talk
basis and is intended for use as:
(a) an ambulatory station; or
(b) a land mobile system station; or
(c) a maritime ship station; or
(d) a citizens band radio station; or
(e) an amateur station.
basic restrictions means the restrictions in
Tables 2 and 6, including the notes to Table 2 and 6, of section 2.3 of the
ARPANSA standard.
device means a mobile station that section 6
or 8 of this Standard apply to.
EN 50361 means
the Basic standard for the measurement of Specific Absorption Rate related
to human exposure to electromagnetic fields from mobile phones – 300MHz to 3GHz
(BS EN 50361:2001) published by the British Standards Institution (BSI) and
assigned the number ISBN 0 580 38460 8.
EN 62209‑1 means 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 hand‑held
devices used in close proximity to the ear (frequency range of 300 MHz to 3
GHz), published by the European Committee for Electrotechnical
Standardisation (CENELEC).
Note EN 62209‑1 is a European Union
harmonised standard based on IEC 62209‑1, a standard developed by
Technical Committee TC106 of the International Electrotechnical Commission
(IEC). Australia has active representation on TC106 through the participation
of Standards Australia (http://www.standards.org.au/).
human body means the head, neck and trunk but
not the limbs.
integral antenna means an antenna:
(a) permanently
attached to equipment; or
(b) intended
for direct attachment to a fixed connector on equipment, without the use of an
external cable.
mobile station means a radiocommunications transmitter that is
established for use:
(a) in
motion, on land, water or in the air; or
(b) in a
stationary position at unspecified points on land, water or in the air.
Examples of a mobile station
1 A
wireless modem operating in a laptop computer.
2 A
hand–held cellular or PCS telephone with a radiating antenna in the handpiece.
non‑aware user device means a device other
than an aware user device.
normal position of use, of a device, means:
(a) the position specified in the measurement
method applicable to the device under section 10, 11 or 12; or
(b) if paragraph (a) does not apply, the
common use spatial orientation of the device with respect to the user; or
(c) if paragraphs (a) and (b) do not apply,
the spatial orientation of the device with respect to the user defined by the
manufacturer.
old standard means the Radiocommunications
(Electromagnetic Radiation — Human Exposure) Standard 2003 as in force
immediately before 1 April 2007.
reference levels means the reference
levels in Table 7 and 8, including the notes to Table 7 and 8, of section 2.4 of the ARPANSA standard.
RF field means a physical field that specifies the
electric and magnetic states of a medium or free space, quantified by the
vectors representing the electric field and the magnetic field.
SAR means Specific Absorption Rate.
(2) A reference in this Standard to a publication or
other document of:
(a) Standards Australia; or
(b) the British Standards Institution; or
(c) the European Committee for Electrotechnical
Standardisation;
includes a reference to the publication or other document as in
force from time to time.
(3) A term that is:
(a) used (but not defined) in this Standard; and
(b) defined in the
Glossary of the ARPANSA standard;
has the meaning given by the Glossary.
6 Application of Standard: general
(1) This Standard applies to a mobile station that:
(a) on or after 1 April 2007, is:
(i) manufactured
or imported; or
(ii) first
offered for supply; or
(iii) altered
or modified in a material respect; and
(b) is capable of
operating in the frequency band 100kHz to 300GHz (inclusive); and
(c) has an integral
antenna; and
(d) is not intended to
be used as an Emergency Position Indicating Radio Beacon (EPIRB) or distress
beacon.
(2) However, this Standard
does not apply to a mobile station that is:
(a) used solely as
equipment, or as part of a weapons system, used by the Defence Force; or
(b) used solely as
equipment, or as part of a weapons system, used by the defence force of another
country that is conducting operations with the Defence Force; or
(c) used solely for
law enforcement activities by any of the following bodies:
(i) the
Australian Federal Police;
(ii) the
National Crime Authority;
(iii) the New
South Wales Crime Commission;
(iv) the
Independent Commission Against Corruption of New South Wales;
(v) the
Criminal Justice Commission of Queensland; or
(d) used solely for law
enforcement activities by a body that:
(i) is not
mentioned in paragraph (c); and
(ii) is
responsible for criminal law enforcement, and established by or under a law of
the Commonwealth, a State or a Territory; or
(e) used solely for
law enforcement activities by a body that:
(i) is not
mentioned in paragraph (c); and
(ii) provides
support for law enforcement in Australia; and
(iii) is responsible or accountable to
the Australian Police Ministers’ Council for the performance of that function;
or
(f) an aware user device or non‑aware user
device that is not mentioned in subsection 10 (1), 11 (1) or
12 (1).
Note 1 Exemptions from the operation of the Act
are also provided for in:
(a) the Act (subsections 24 (1) and (2) and
section 25); and
(b) the Radiocommunications Regulations 1993
(regulation 6).
The exemptions
relate to activities of the Defence Force, the Australian Security Intelligence
Service and the Australian Security Intelligence Organisation.
Note 2 The application of this Standard to a
device under this section is not relevant to the definition of non‑standard
device in section 9 of the Act because the status of the device (as standard or
non‑standard) was established when the device was last manufactured,
imported, altered or modified.
7 Transitional
arrangements on and after 1 April 2007
On and after 1 April 2007, the old standard
continues to apply to a mobile station if:
(a) the device is not
equipment to which this Standard applies under section 6; and
(b) the old standard
applied to the device immediately before 1 April 2007.
Note 1 The continued application
of this Standard to a device under this section is not relevant to the
definition of non‑standard device in section 9 of the Act
because the status of the device (as standard or non‑standard) was
established when the device was last manufactured, imported, altered or
modified.
Note 2 For paragraph (a)
a device that was manufactured, imported, altered or modified before 1 April
2007 is equipment to which this Standard does not apply under section 6.
9 Performance
standards
(1) For paragraph 162 (1) (a) of the Radiocommunications
Act 1992, the standard for performance for an aware user device to which
subsection 6 (1) of this
Standard applies is that the device must not expose the user to electromagnetic
radiation at a level greater than the basic restrictions for occupational
exposure when the device is used in its normal position of use.
(2) For paragraph 162 (1) (a) of the Radiocommunications
Act 1992, the standard for performance for a non–aware user device to which
subsection 6 (1) of this
Standard applies is that the non–aware user device must not expose the user to
electromagnetic radiation at a level greater than the basic restrictions for
general public exposure when the device is used in its normal position of use.
10 Measurement
methods for performance standards: aware user device or non‑aware user
device in close proximity to the human ear
(1) This section applies to an aware user device or non‑aware
user device to which this Standard applies that:
(a) is designed to be used, or held with the
radiating part of the aware user device or non‑aware user device in close
proximity to the human ear; and
(b) transmits on a frequency in the frequency
band 300MHz to 3GHz (inclusive).
(2) Before 1 March 2009, the measurements to determine
if the aware user device or non‑aware user device meets the standard for
performance of subsection 9 (1) or 9 (2) are the measurements in EN 50361,
Schedule 2 or EN 62209‑1.
(3) On and after 1 March 2009, the measurements to
determine if the aware user device or non‑aware user device meets the
standard for performance of subsection 9 (1) or 9 (2) are the measurements in
EN 62209‑1.
11 Measurement
methods for performance standards : aware user device or non–aware user device
20cm or less from the human body
(1) This section applies to an aware user device or a non–aware
user device to which this Standard applies that:
(a) is designed to be used, or held with the
radiating part of the aware user device or non‑aware user device in close
proximity to the human body but not more than 20cm from the human body; and
(b) transmits on a frequency in the frequency
band 150MHz to 5.8GHz (inclusive); and
(c) is not mentioned in subsection 10 (1).
(2) The measurements to determine if the aware user
device or non‑aware user device meet the standard for performance of
subsection 9 (1) or 9 (2) are the measurements in Schedule 2.
(3) A test report must comply with the requirements in
Schedule 2.
12 Assessment methods for performance
standards: aware user devices and non‑aware user devices more than 20cm
from the human body
(1) This section applies to an aware user device or a
non‑aware user device to which this Standard applies that:
(a) is designed to be used, or held, more than
20cm from the human body; and
(b) transmits in the frequency band 300kHz to
100GHz (inclusive).
(2) The RF field produced by an aware user device or a
non‑aware user device, at the position of the user with the device
operated at the normal position of use, must be assessed in accordance with the
requirements in AS 2772.2.
(3) An aware user device is taken to meet the standard
for performance of subsection 9 (1) if the RF field assessed under
subsection (2) is less than the relevant reference levels for occupational
exposure.
(4) A non‑aware user device is taken to meet the
standard for performance of subsection 9 (2) if the RF field assessed is
less than the relevant reference levels for general public exposure.
Schedule
2 Measurement method for devices 20cm
or less from the human body
(subsection 11 (2))
Part 1 Information for
documenting SAR compliance
1.1 General
1.1.1 The information
described in this Part must be included in test reports. The information is necessary
to evaluate test results and to determine RF exposure compliance.
1.2 Information on
test device and exposure categories
1.2.1 The following
information on test device operating configurations and test conditions for SAR
measurements must be included in a test report:
(a) a description of
the device, including model number where applicable;
(b) a
brief description of the test device operating configurations; including:
(i) operating
modes and operating frequency range(s);
(ii) maximum conducted
power for each operating mode and frequency range;
(iii) operating
conducted power tolerances;
(iv) antenna
type and operating positions;
(v) applicable
body–worn configurations;
(vi) battery
options that could affect the SAR results;
(vii) procedures
used to establish the test signals;
(viii) applicable
source‑based time‑averaging duty factor and the duty factor used in
the tests;
(ix) maximum
output power measured before and after each SAR test or SAR drift measurements
(see 3.13.1).
1.3 Specific Information
for SAR Measurements
1.3.1 The report must
set out the measurement system and site description including:
(a) a brief
description of the SAR measurement system;
(b) a brief description
of the test set up.
1.3.2 The report must
set out the electric field probe calibration including:
(a) a description of
the probe, its dimensions and sensor offset etc;
(b) a description of
the probe measurement uncertainty;
(c) the most recent
calibration date.
1.3.3 The report must
set out the SAR measurement system verification including:
(a) a brief
description of the RF radiating source used to verify the SAR system
performance within the operating frequency range of the test device (see Part
3);
(b) a list of the
tissue dielectric parameters, ambient and tissue temperatures, output power,
peak and ten‑gram averaged SAR for the measured and expected target test
configurations;
(c) a list of the
error components contributing to the total measurement uncertainty.
1.3.4 The report must
set out the phantom description including:
(a) a description of
the head and body phantoms used in the tests, including shell thickness and
other tolerances.
1.3.5 The report must
set out the tissue dielectric property including:
(a) the composition of
the ingredients for the tissue material used in the SAR tests;
(b) the tissue
dielectric parameters measured at the middle of each operating frequency range
of the test device;
(c) the temperature
range and operating conditions of the tissue material during each SAR measurement.
1.3.6 The report must
set out the positioning of the device including:
(a) a description of
the dielectric holder or similar mechanisms used to position the test device in
the specific test configurations;
(b) a description of
the positioning procedures used to evaluate the highest exposure expected under
normal operating configurations;
(c) sketches and
illustrations showing the device positions, with respect to the phantom;
including separation distances and angles, as appropriate;
(d) a description of
the antenna operating positions, extended, retracted or stowed etc. and the
configurations tested in the SAR evaluation.
1.3.7 The report must
set out the peak SAR locations including:
(a) a description of
the coarse resolution, surface or area scan procedures used to search for all
possible peak SAR locations within the phantom;
(b) a description of
the interpolation procedures applied to the measured points to identify the
peak SAR locations at a finer spatial resolution;
(c) a description,
illustration and SAR distribution plots showing the peak SAR locations with
respect to the phantom and the test device;
(d) identify the peak
SAR locations used to evaluate the highest ten‑gram averaged SAR.
1.3.8 The report must set out
the ten‑gram averaged SAR
including:
(a) a description of
the fine resolution, volume or zoom scan procedures used to determine the
highest ten‑gram averaged SAR in the shape of a cube;
(b) a
description of the extrapolation procedures used to estimate the SAR value of
points close to the phantom surface that are not measurable;
(c) a description of
the interpolation procedures applied to the measured and extrapolated points to
obtain SAR values at a finer spatial resolution within the zoom scan volume;
(d) a description of
the integration procedures applied to the interpolated SAR values within the
zoom scan volume to determine the highest ten‑gram SAR in the shape of a
cube.
1.3.9 The report must set out the total measurement
uncertainty including:
(a) a tabulated list
of the error components and uncertainty values contributing to the total
measurement uncertainty (see Part 3);
(b) reporting the combined standard uncertainty
and expanded uncertainty (for 95% confidence interval) of each measurement.
1.3.10 The
report must set out the test results for determining SAR compliance including:
(a) if the channels tested for each
configuration (left, right, cheek, tilt/ear, extended, retracted etc.) have
similar SAR distributions, a plot of the highest SAR for each test configuration
should be sufficient; otherwise additional plots should be included to document
the differences;
(b) all of the measured
SAR values should be documented in a tabulated format with respect to the test
configurations.
Part 2 Tissue Dielectric Parameters
2.1 General
2.1.1 The head and body tissue parameters given in
this Part should be used to test transmitters
operating in the cellular, PCS, U‑NII, spread spectrum and other
frequencies bands (See Reference [1], [3] and [4]). When
a transmission band overlaps with one of the target frequencies specified in
this Part, the tissue dielectric parameters of the tissue medium at the middle
of a device transmission band should be within 5% of the parameters specified
at that target frequency. At other frequencies, the dielectric parameters
should be linearly interpolated between the closest pair of target frequencies
specified in this Part to determine the applicable dielectric parameters
corresponding to the middle of a device transmission band. It has been
reported that a 5% tolerance in tissue parameters may not be easily achieved at
certain frequencies. Under such circumstances, 10% tolerance may be used until
more precise tissue recipes are available.
2.2 Tissue Dielectric Parameters for Head and
Body Phantoms
2.2.1 The head tissue dielectric parameters
recommended by the IEEE SCC‑34/SC‑2 in P1528 [6] have been
incorporated in the following table. These head parameters are derived from
planar layer models simulating the highest expected SAR for the dielectric
properties and tissue thickness variations in a human head (See Reference [2]). Other head and body tissue
parameters that have not been specified in P1528 are derived from the tissue
dielectric parameters computed from the 4‑Cole‑Cole equations
described in Reference [3] and extrapolated
according to the head parameters specified in P1528 [6].
|
Target
Frequency
|
Head
|
Body
|
|
(MHz)
|
er
|
s (S/m)
|
er
|
s (S/m)
|
|
150
|
52.3
|
0.76
|
61.9
|
0.80
|
|
300
|
45.3
|
0.87
|
58.2
|
0.92
|
|
450
|
43.5
|
0.87
|
56.7
|
0.94
|
|
835
|
41.5
|
0.90
|
55.2
|
0.97
|
|
900
|
41.5
|
0.97
|
55.0
|
1.05
|
|
915
|
41.5
|
0.98
|
55.0
|
1.06
|
|
1450
|
40.5
|
1.20
|
54.0
|
1.30
|
|
1610
|
40.3
|
1.29
|
53.8
|
1.40
|
|
1800 – 2000
|
40.0
|
1.40
|
53.3
|
1.52
|
|
2450
|
39.2
|
1.80
|
52.7
|
1.95
|
|
3000
|
38.5
|
2.40
|
52.0
|
2.73
|
|
5800
|
35.3
|
5.27
|
48.2
|
6.00
|
(er = relative permittivity, s = conductivity and r = 1000 kg/m3)
2.3 Typical Composition of Ingredients for
Liquid Tissue Phantoms
2.3.1 The following
tissue formulations are provided for reference only as some of the parameters
have not been thoroughly verified. The composition of ingredients may be
modified accordingly to achieve the desired target tissue parameters required
for routine SAR evaluation.
|
Ingredients
(% by weight)
|
Frequency
(MHz)
|
|
450
|
835
|
915
|
1900
|
2450
|
|
Tissue Type
|
Head
|
Body
|
Head
|
Body
|
Head
|
Body
|
Head
|
Body
|
Head
|
Body
|
|
Water
|
38.56
|
51.16
|
41.45
|
52.4
|
41.05
|
56.0
|
54.9
|
40.4
|
62.7
|
73.2
|
|
Salt (NaCl)
|
3.95
|
1.49
|
1.45
|
1.4
|
1.35
|
0.76
|
0.18
|
0.5
|
0.5
|
0.04
|
|
Sugar
|
56.32
|
46.78
|
56.0
|
45.0
|
56.5
|
41.76
|
0.0
|
58.0
|
0.0
|
0.0
|
|
HEC
|
0.98
|
0.52
|
1.0
|
1.0
|
1.0
|
1.21
|
0.0
|
1.0
|
0.0
|
0.0
|
|
Bactericide
|
0.19
|
0.05
|
0.1
|
0.1
|
0.1
|
0.27
|
0.0
|
0.1
|
0.0
|
0.0
|
|
Triton X‑100
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
36.8
|
0.0
|
|
DGBE
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
44.92
|
0.0
|
0.0
|
26.7
|
|
Dielectric Constant
|
43.42
|
58.0
|
42.54
|
56.1
|
42.0
|
56.8
|
39.9
|
54.0
|
39.8
|
52.5
|
|
Conductivity (S/m)
|
0.85
|
0.83
|
0.91
|
0.95
|
1.0
|
1.07
|
1.42
|
1.45
|
1.88
|
1.78
|
Salt: 99+% Pure
Sodium Chloride Sugar: 98+% Pure Sucrose
Water: De‑ionized, 16 MW+
resistivity HEC: Hydroxyethyl Cellulose
DGBE: 99+%
Di(ethylene glycol) butyl ether, [2‑(2‑butoxyethoxy)ethanol]
Triton X‑100 (ultra
pure): Polyethylene glycol mono [4‑(1,1, 3, 3‑tetramethylbutyl)phenyl]ether
Tissue Recipe as reported by
Hartsgrove et. al. in “Simulated Biological Materials for Electromagnetic
Radiation absorption Studies,” Bioelectromagnetics 8:29‑36 (1987)
|
Ingredients
(% by weight)
|
Head/Brain
|
Body/Muscle
|
|
Water
|
40.4
|
52.5
|
|
Salt
(NaCl)
|
2.5
|
1.4
|
|
Sugar
|
56.0
|
45.0
|
|
HEC
|
1.0
|
1.0
|
|
Bactericide
|
0.1
|
0.1
|
|
Dielectric
constant @ 900 MHz
|
41.2
|
54.7
|
|
Conductivity
@ 900 MHz (S/m)
|
1.22
|
1.38
|
Part 3 SAR measurement procedures
3.1 General
3.1.1 The SAR measurement procedures described in
this Part are primarily intended for testing wireless handsets and similar
transmitters that operate next to a person’s head. The test configurations for
evaluating body‑worn SAR compliance are also described.
3.1.2 SAR is evaluated using simulated tissue
medium contained in a realistic human shaped phantom shell that allows a small
diameter, miniature electric field probe to measure the electric field within
the tissue regions exposed to the transmitter configured in normal operating
positions. Since the RF energy absorption characteristics of human tissues are
frequency dependent, the dielectric properties of simulated tissue media used
for SAR evaluations must match the target tissue properties specified at the
operating frequency range of the device (See Part 2).
3.2 Phantom Considerations
3.2.1 Handsets that are held on the side of a
person's head next to the ear have been tested using two general types of
realistic‑shaped head phantoms: with and without a simulated external ear
attached to the head model. A simulated ear with a thickness of approximately
2‑3 mm, consisting of low‑loss dielectric material has been used to
model a person's ear compressed by the earpiece of a wireless handset on some
head models. Others have used a 2‑4 mm thick, circular shaped, low‑loss
dielectric spacer to simulate the ear separation distance.
3.2.2 The IEEE SCC‑34/SC‑2 has
established criteria for developing a standardized head model to test handsets
for SAR compliance. This head model has been derived from selected head
dimensions of male, U.S. Army personnel (See Reference
[8]). The committee has specified the phantom shell to be constructed of low‑loss
dielectric material with dielectric constant less than 5.0 and loss tangent not
exceeding 0.05. The thickness of the phantom shell should be 2.0 mm with less
than ± 0.2 mm variations in shape and
thickness for regions where SAR is to be measured and ± 0.5 mm for other regions. A 4.0 mm thick low‑loss
dielectric spacer is used to simulate the ear separation distance on this head
model.
3.2.3 A reference plane has been defined by three
points consisting of a point on each ear spacer and the tip of the mouth to
minimize test device positioning errors. The points on each ear spacer are
known as the ear reference points; each is located at 1.5 cm above the ear
canal location in the reference plane. During SAR measurements, the centreline
on the front of a handset is aligned to this predefined reference plane and the
earpiece is positioned at the level of the ear reference point. The ear spacer
is tapered abruptly to zero thickness below the ear reference point, along a
line perpendicular to the reference plane. By using a standardized head model
with specific ear simulation requirements, device positioning errors are
reduced and lower SAR measurement uncertainty is expected (See Reference [6]).
3.2.4 The construction of a liquid phantom must
allow unrestricted electric field probe access to search for all possible peak
SAR locations produced by a portable transmitter under test. The tissue
material within the phantom shell measured from the ear reference point should
be at least 15 cm deep. In most situations, split head models are used to test
transmitters on the left and right side of the head. A separate flat phantom
should be used to test exposures in body‑worn configurations and other
body regions that are relatively flat, such as the chest and abdomen.
3.3 Recommended
Characteristics of Head and Body Phantoms
3.3.1 The following information provides
additional guidance on head and body models that are considered acceptable for
routine evaluation of most wireless handsets and similar portable
transmitters. The SCC‑34/SC‑2 head conforms to the relevant
portions of these criteria:
(a) the shape, dimensions and complexity of a
human shaped head phantom should be appropriate for evaluating the near‑field
exposure conditions expected by the users of a transmitter device under normal
operating conditions;
(b) the head phantom should include a portion of
the neck, preferably extending to the base of the neck. Shoulders are not
necessary;
(c) body‑worn operating configurations
should be tested using a flat phantom. The length and width of the phantom
should be at least twice the corresponding dimensions of the test device,
including its antenna. The body dielectric parameters specified in Part 2
should be used to demonstrate body‑worn SAR compliance;
(d) the head and body phantom shell should be
made of low‑loss dielectric material with dielectric constant and loss
tangent less than 5.0 and 0.05 respectively. The shell thickness for all
regions coupled to the test device and its antenna should be within 2.0 ± 0.2 mm. The phantom should be filled with
the required head or body equivalent tissue medium to a depth of 15.0 ± 0.5 cm.
3.4 Recommended
device test positions for typical Wireless Handset
3.4.1 Specific test
positions have been prescribed by the SCC‑34/SC‑2 for testing
handsets using the standardized head model recommended by this committee. For
routine SAR evaluation, these test positions, as described below, should be
used for testing handsets and similar portable transmitters that operate on the
side of a person’s head, next to the ear. Flat phantom models should be used
to test handsets and push‑to‑talk (PTT) devices that can be held in
front of the user’s face or transmit in body‑worn operating
configurations using belt‑clips, holsters or similar accessories. The
test device should be placed in a holder or positioner made of low‑loss
dielectric material with dielectric constant and loss tangent less than 5.0 and
0.05 respectively. If the device holder is suspected to perturb the fields
from the test device, which may affect device performance or introduce
unacceptable SAR measurement errors, such as handsets with internal antennas,
the error must be assessed and accounted for in the total measurement
uncertainty. Device holder perturbation may be verified by testing the device
on a flat phantom in each frequency band and antenna position with and without
using the holder.
3.5 Devices
operating next to a person’s ear
3.5.1 This category includes most wireless
handsets with fixed, retractable or internal antennas located toward the top
half of the device, with or without a foldout, sliding or similar keypad
cover. The handset should have its earpiece located within the upper ¼ of the
device, either along the centreline or off‑centred, as perceived by its
users. This type of handset should be positioned in a normal operating
position with the “test device reference point” located along the “vertical
centreline” on the front of the device aligned to the “ear reference point” (See Reference [6]). The “test device reference
point” should be located at the same level as the centre of the earpiece
region. The “vertical centreline” should bisect the front surface of
the handset at its top and bottom edges. A “ear reference point” is
located on the outer surface of the head phantom on each ear spacer. It is
located 1.5 cm above the centre of the ear canal entrance in the “phantom
reference plane” defined by the three lines joining the centre of each “ear
reference point” (left and right) and the tip of the mouth (See Reference [6]). The terms “test device reference point”,
“vertical centerline”, “ear reference point”, “phantom
reference plane” and “initial ear position” are specific references
used to align a test device to the head phantom.
3.5.2 A handset should be initially positioned
with the earpiece region pressed against the ear spacer of a head phantom. For
the SCC‑34/SC‑2 head phantom, the device should be positioned
parallel to the “N‑F” line defined along the base of the ear spacer that
contains the “ear reference point”. The “test device reference point” is aligned
to the “ear reference point” on the head phantom and the “vertical centreline”
is aligned to the “phantom reference plane”. This is called the “initial
ear position”. While maintaining these three alignments, the body of the
handset is gradually adjusted to each of the following positions for evaluating
SAR:
(a) “Cheek/Touch Position” – the device is
brought toward the mouth of the head phantom by pivoting against the “ear
reference point” or along the “N‑F” line for the SCC‑34/SC‑2
head phantom. This test position is established:
(i) when any
point on the display, keypad or mouthpiece portions of the handset is in
contact with the phantom; or
(ii) when any portion of a foldout,
sliding or similar keypad cover opened to its intended self‑adjusting normal
use position is in contact with the cheek or mouth of the phantom.
(b) “Ear/Tilt
Position” – with the handset aligned in the “Cheek/Touch Position”:
(i) if
the earpiece of the handset is not in full contact with the phantom’s ear
spacer (in the “Cheek/Touch position”) and the peak SAR location for the
“Cheek/Touch” position is located at the ear spacer region or corresponds to
the earpiece region of the handset, the device should be returned to the
“initial ear position” by rotating it away from the mouth until the earpiece is
in full contact with the ear spacer; or
(ii) the
handset should be moved (translated) away from the cheek perpendicular
to the line passes through both “ear reference points” (note: one of these ear
reference points may not physically exist on a split head model) for
approximate 2‑3 cm. While it is in this position, the device handset is tilted away from the mouth with
respect to the “test device reference point” until
the inside angle between the vertical centerline on the front surface of the
phone and the horizontal line passing through the ear reference point is by
15 80°. After the tilt, it is then moved
(translated) back toward the head perpendicular to the line passes through both
“ear reference points” until the device touches the phantom or the ear spacer.
If the antenna touches the head first, the positioning process should be
repeated with a tilt angle less than 15 80°
so that the device and its antenna would touch the phantom simultaneously.
This test position may require a device holder or positioner to achieve the
translation and tilting with acceptable positioning repeatability.
3.5.3 If a device is also designed to transmit
with its keypad cover closed for operating in the head position, such positions
should also be considered in the SAR evaluation. The device should be tested
on the left and right side of the head phantom in the “Cheek/Touch” and
“Ear/Tilt” positions. When applicable, each configuration should be tested
with the antenna in its fully extended and fully retracted positions. These
test configurations should be tested at the high, middle and low frequency
channels of each operating mode; for example, AMPS, CDMA, and TDMA. If the SAR
measured at the middle channel for each test configuration (left, right,
Cheek/Touch, Tile/Ear, extended and retracted) is at least 3.0 dB lower than
the SAR limit, testing at the high and low channels is optional for such test
configuration(s). If the transmission band of the test device is less than 10
MHz, testing at the high and low frequency channels is optional. A complete
set of tests for a handset operating with a retractable antenna has 24
configurations for each operating mode, as shown in the following table:
Recommended handset and head phantom test positions for FCC
compliance evaluation
|
Phantom Configurations
|
Device Test Positions
|
Antenna Position
|
SAR (W/kg)
Device Test channel, Frequency
& Output
|
|
Channel: ___
___ MHz
___ mW
|
Channel: ___
___ MHz
___ mW
|
Channel: ___
___ MHz
___ mW
|
|
Left Side of
Head
|
Cheek / Touch
|
extended
|
|
|
|
|
retracted
|
|
|
|
|
Ear / Tilt
|
extended
|
|
|
|
|
retracted
|
|
|
|
|
Right Side of Head
|
Cheek / Touch
|
extended
|
|
|
|
|
retracted
|
|
|
|
|
Ear / Tilt
|
extended
|
|
|
|
|
retracted
|
|
|
|
3.6 Recommended test positions for body‑worn
and other configurations
3.6.1 Body‑worn operating configurations
should be tested with the belt‑clips and holsters attached to the device
and positioned against a flat phantom in normal use configurations. Devices
with a headset output should be tested with a headset connected to the device.
The body dielectric parameters specified in Part 2 should be used. Both the
physical spacing to the body of the user as dictated by the accessory and the
materials used in an accessory affect the SAR produced by the transmitting
device. For purpose of determining test requirements, accessories may be
divided into two categories: those that do not contain metallic components and
those that do.
3.6.2 When multiple accessories that do not
contain metallic components are supplied with the device, the device may be
tested with only the accessory that dictates the closest spacing to the body.
When multiple accessories that contain metallic components are supplied with
the device, the device must be tested with each accessory that contains a
unique metallic component. If multiple accessories share an identical metallic
component (e.g., the same metallic belt‑clip used with different holsters
with no other metallic components), only the accessory that dictates the
closest spacing to the body must be tested.
3.6.3 Body‑worn accessories may not always
be supplied or available as options for some devices that are intended to be
authorized for body‑worn use. A separation distance of 1.5 cm between
the back of the device and a flat phantom is recommended for testing body‑worn
SAR compliance under such circumstances. Other separation distances may be
used, but they should not exceed 2.5 cm. In these cases, the device may use
body‑worn accessories that provide a separation distance greater than
that tested for the device provided however that the accessory contains no
metallic components..
3.6.4 Transmitters that are designed to operate in
front of a person’s face, in push‑to‑talk configurations, should be
tested for SAR compliance with the front of the device positioned at 2.5 cm
from a flat phantom. Frontal face‑phantoms are typically not recommended
because of the potential of higher E‑field probe boundary‑effects
errors in the non‑smooth regions of these face phantoms, such as the nose,
lips and eyes etc. For devices that are carried next to the body, such as
shoulder, waist or chest‑worn transmitters, SAR compliance should be
tested with the accessories, including headsets and microphones, attached to
the device and positioned against a flat phantom in normal use configurations.
3.7 Documentation
3.7.1 Device test positions should be documented
graphically and identify the separation distances and tilt angles used during
the SAR evaluation. This will allow, if necessary, the test to be repeated
accurately with the device positioned as specified in the test report. A close‑up
photo(s) of the actual test device positioned against the phantom during the
SAR measurement should also be included in the test report to document the test
setup.
3.8 Tissue
Dielectric Property Requirements
3.8.1 The tissue media should be checked at the
beginning of a series of SAR measurements to determine if the dielectric
parameters are within the tolerances of the specified target values. The
dielectric parameters should be verified daily and more often as required by
the ambient conditions. For example, when the liquid temperature deviates by
more than 2°C from that recorded for the measured dielectric parameters and
under conditions of extremely low humidity or high evaporation rates. The
tissue parameters should be measured with the coaxial probe, slotted line or
TEM line techniques described in the SCC‑34/SC‑2 SAR measurement
document (See Reference [6]).
3.8.2 The tissue dielectric parameters specified
in Part 2 should be used as the target values for testing (See References [2], [3] and [6]). These parameters are
generally accepted as equivalent to the corresponding tissue properties at 37°C, for use in single‑tissue
homogeneous phantom models. Examples of the typical composition of ingredients
used to achieve these parameters under normal ambient conditions are also
included in Part 2. The use of other compositions and formulations to arrive
at the same tissue parameters may also be acceptable. SAR measurements should
be performed under normal ambient conditions, suitable for the test equipment,
typically within 20‑26° C and 30‑70%
humidity. The temperature of the tissue medium during the SAR measurement
should be within ± 2.0°C of the temperature at which the dielectric
parameters are measured. The relative permittivity and conductivity of the
tissue material should be within 5% of the values given in Part 2, 10% when
precise tissue recipes are not available at certain frequencies. Transmitters
operating at other frequencies should be tested using tissue parameters based
on the linearly interpolated values shown in Part 2, corresponding to the mid‑band
frequency of each operating mode. The instrumentation error associated with
the measured tissue parameters should be accounted for in the overall SAR
measurement uncertainty.
3.9 Electric Field
Probe Characteristics and Calibration
3.9.1 The E‑field probes used for SAR
measurements should have a dynamic range of 0.01‑100 W/kg to cover the
range of signal levels and modulation characteristics used by most mobile
stations. The field probes used in SAR measurements are typically calibrated
to measure single frequency fields. The probe output follows the square‑law
response of its detectors at low field strength levels. As the field strength
level increases, special circuitry or compensation software are used to achieve
a linear response. When measuring pulsed signals with low duty factors or high
peak‑to‑average ratios, the probe must be calibrated with
correction factors to accurately measure SAR with respect to the average
power. If the signal level exceeds the square‑law response of the diode
detectors in an E‑field probe, the output can become sensitive to the
signal modulation and the error is usually dependent on the form of
modulation. A probe must be properly calibrated to measure the SAR
corresponding to the average energy absorption produced by a modulated signal.
A probe linearity of ± 0.25 dB should
be ensured at the device test frequencies during routine SAR evaluation.
3.9.2 The variation in sensitivity among the
sensors in a field probe must be correctly compensated for during probe
calibration. It is highly desirable for a probe to have a uniform response to
all incident fields, independent of field polarization and direction of
propagation. However, the isotropic response of a probe is often non‑ideal
due to construction tolerances, asymmetry in sensor location, differences in
detector sensitivity among the channels, differences in line impedance and
feedback from the feed lines. It is extremely important that these undesirable
characteristics are carefully evaluated during probe calibrations by rotating
the probe along its axis and orienting the probe and its sensors to different
field polarizations and directions of propagation. The axial and hemispherical
isotropy errors of a probe should be within ±
0.25 and ± 0.5 dB, respectively, at the
device test frequencies during routine SAR measurement.
3.9.3 A field probe must be calibrated in tissue
media with the target dielectric parameters specified in Part 2, corresponding
to the operating frequency ranges of the test device. The responses of a field
probe are dependent on signal frequency, modulation characteristics, power
level, field polarization, field gradients and the direction of field
propagation. Other factors such as RF noise, static and ELF fields,
temperature, humidity and the proximity of media boundaries from the probe tip
can also affect the calibration of a field probe. At less than 800 MHz, probes
are calibrated using thermal techniques. At above 800 MHz, an appropriate
waveguide filled with the required tissue medium may be used to calibrate the
output voltages of a probe against analytically calculated field values (See References [5], [6] and [7]).
3.10 System Verification
3.10.1 Routine record keeping procedures
should be established for tracking the calibration and performance of SAR
measurement systems. When SAR measurements are performed, the entire
measurement system should be checked daily within the device transmitting
frequency ranges to verify system accuracy. A flat phantom irradiated by a
half‑wavelength dipole is typically used to verify the measurement
accuracy of a system. The measurement system should also be evaluated
periodically with and without the built‑in compensation and correction
factors to verify the measurement sensitivity and to identify system components
that could be out of tolerance. When a radiating source is not available at
the operating frequency range of the test device to verify system accuracy, a
source operating within 100 MHz of the mid‑band channel of each operating
mode may be used. The measured ten‑gram SAR should be within 10% of the
expected target values specified for the specific phantom and RF source used in
the system verification measurement.
3.10.2 The following describes the recommended test
configuration for verifying SAR measurement systems using a flat phantom and a
dipole radiating source to determine if the system meets its performance (Note:
systems may be verified at 300 MHz until standard dipoles at below 300 MHz are
available):
(a) A balanced half‑wave (l/2) dipole should be used as the radiating
source. The dipole should be matched to the source impedance of the signal
generator. The specific flat phantom should be filled with the required tissue
medium at its intended operating frequency. The current distribution along the
two arms of the half‑wave dipole should be matched to within 5% of each
other. The thickness of the dipole must not exceed the separation distance
between the outer surfaces of the dipole and the phantom shell by 20%. The
construction of the dipole should provide extremely stable operating
characteristics at its intended operating frequency to produce repeatable SAR
distributions in the specific flat phantom. The recommended dipole specifications
described in the latest SCC‑34/SC‑2 draft on SAR measurement
procedures should be used (See Reference [6]).
(b) Before the dipole can be used to verify the
performance of SAR measurement systems, its radiating characteristics must be
fully characterized at the intended operating frequency.
(c) The phantom shell (or box) should be
constructed of low‑loss dielectric material with dielectric constant less
than 5 and loss tangent less than 0.05. The material thickness on the side
that couples to the dipole (the bottom) must not be thicker than 6.5 mm for use
at below 1.0 GHz and 5.0 mm at other frequencies. The variations in shell
thickness along regions coupled to the dipole must be less than ± 0.2 mm. The material for the other sides
must not be thicker than 10 mm.
(d) The phantom should be at least ¾ wavelength
long, in the direction parallel to the dipole and ½ wavelength wide, in the
direction perpendicular to the dipole. Smaller phantom dimensions may be
acceptable if it can be demonstrated that the measured ten‑gram SAR is
within ± 1% of that produced by a
phantom with the required phantom dimensions. The phantom should hold 15 ± 0.5 cm of the required tissue medium.
(e) The SAR system should be verified using this
flat phantom setup, preferably, at the mid‑band frequency of a test
device, but not more than 100 MHz from this frequency.
(f) The dielectric parameters of the tissue
medium used to verify the SAR system should be within 5% of those used to
obtain the reference data (target SAR values) and should also satisfy the
requirements specified in Part 2.
(g) A uniform separation distance of 15.0 mm ± 0.2 mm should be maintained between the
dipole axis and the inside surface of the phantom shell (tissue medium surface)
at the dipole feed‑point location. At above 1.0 GHz, a separation
distance of 10.0 mm ± 0.2 mm should be
used. A precision low‑loss dielectric spacer and holding apparatus
should be used to maintain dipole positioning repeatability.
(h) Each end of the dipole should not deviate by
more than 2° from the dipole axis with
respect to the dipole feed‑point. The sagging of the phantom, due to the
weight of the tissue medium, at its closest location to the dipole feed‑point
should be within 1° from the straight
line joining the two points on the phantom that are closest to the ends of the
dipole, with respect to each of these points on the phantom.
(i) The measured ten‑gram SAR at the
surface of the phantom above the dipole feed‑point should be within 10%
of the target reference value. The SAR distribution must be identical to the
reference data.
(j) Since the dielectric properties of the
phantom shell and its thickness along regions coupled to the dipole may affect
the dipole impedance and the measured SAR values, the target SAR values may
only be applicable for the specific combination of dipole and flat phantom
configuration. The following table contains a summary of the acceptable range
of dipole and phantom separation distances for the dipole dimensions described
in P1528.
Dipole Thickness, Flat Phantom Sagging and Separation
Distance Requirements
|
Frequency
(MHz)
|
Dipole Length
|
Half of
Dipole
Length
|
2 °
Dipole
Deviation
|
1 °
Phantom
Sagging
|
Maximum
Shell
Thickness
|
Dipole
to Tissue
Separation
|
Max.
Dipole
Dia.
|
Min.
Air
Gap
|
0.5% of
0.6 l
(Sagging)
|
|
300
|
420.0
|
210.0
|
7.3
|
3.67
|
6.5
|
15.0
|
6.4
|
5.3
|
3.00
|
|
450
|
288.0
|
144.0
|
5.0
|
2.51
|
6.5
|
15.0
|
6.4
|
5.3
|
2.00
|
|
835
|
161.0
|
80.5
|
2.8
|
1.41
|
6.5
|
15.0
|
6.4
|
5.3
|
1.08
|
|
900
|
149.0
|
74.5
|
2.6
|
1.30
|
6.5
|
15.0
|
6.4
|
5.3
|
1.00
|
|
1450
|
89.1
|
44.6
|
1.6
|
0.78
|
5.0
|
10.0
|
3.8
|
3.1
|
0.62
|
|
1800
|
72.0
|
36.0
|
1.3
|
0.63
|
5.0
|
10.0
|
3.8
|
3.1
|
0.50
|
|
1900
|
68.0
|
34.0
|
1.2
|
0.59
|
5.0
|
10.0
|
3.8
|
3.1
|
0.47
|
|
2000
|
64.5
|
32.3
|
1.1
|
0.56
|
5.0
|
10.0
|
3.8
|
3.1
|
0.45
|
|
2450
|
51.8
|
25.9
|
0.9
|
0.45
|
5.0
|
10.0
|
3.8
|
3.1
|
0.37
|
|
3000
|
41.5
|
20.8
|
0.7
|
0.36
|
5.0
|
10.0
|
3.8
|
3.1
|
0.30
|
(all dimensions in mm)
3.11 Test Site Ambient Conditions
3.11.1 The RF interference characteristics and
ambient conditions at a test facility should be fully characterized to
determine their influences on the SAR measurement. RF noise may enter the
measurement equipment either by conduction through cables or through radiated
fields. These unwanted signals may be rectified by metal‑to‑metal
junctions and semiconductor devices resulting in DC offsets or low frequency
signals that cannot be separated from the desired signal detected by the
electric field probe. Other conditions such as ground loops and cable
conditions that can change the loading conditions of the instrumentation,
resulting in noise or oscillation, should also be evaluated regularly. These
conditions should be checked daily before SAR measurements are performed. The
impact of RF interference on SAR measurements may be verified by performing a
SAR measurement with the test device powered off. During compliance
measurements, the RF environment should be closely monitored to ensure
measurement accuracy. The ambient conditions at a test site, such as the
temperature and humidity, may affect the operating stability of the measurement
equipment and tissue dielectric parameters. These conditions should also be closely
monitored during each SAR measurement to ensure measurement accuracy.
3.12 Test Device Operating Conditions
3.12.1 Most handsets and portable transmitters are
battery operated. The devices should operate with a fully charged battery for
each SAR test. The performance and operating tolerances of a test device
should be fully characterized to ensure that it is identical to the production
units for meeting compliance. The output power of the test sample should not
be set using test software or test mode sequences to artificially higher or
lower output levels than those pre‑programmed for production units.
Transmitters should be tested at the maximum output level for normal operation
within the intended wireless networks, to avoid undesirable performance issues
that could lead to SAR changes. The measured SAR values may be scaled to cover
certain output tolerances expected among production units during normal use
provided the scaled values are within 5% of the measured values. Unless an
external DC power adapter or other signal leads are required for the normal
operation of a device, such as connecting a headset to the device for body‑worn
use, they should not be used in the SAR tests.
3.13 Output Power
3.13.1 In order to determine if device output has been
stable during a SAR measurement, conducted power should be measured before and
after each SAR test to verify if the output changes are within the tolerance
specified for the device. Conducted output power can be measured at a service
output port available on most handsets or with an antenna adapter.
Alternatively, the SAR should be checked at a reference location, such as above
the ear reference point of the head phantom, immediately before and after each
SAR measurement to verify device output and SAR drifts.
3.14 Battery Options
3.14.1 Most wireless handsets and portable
transmitters may operate with several battery options, such as internally built‑in
batteries, standard battery packs, a slim pack to save space or a long lasting
pack for extended use without frequent recharging. These batteries often have
different cell configurations and physical dimensions. In some situations, the
battery design may cause some device performance and SAR variations. If the
radiated output power of a handset varies with its battery options, the
corresponding SAR may also change. An increase in radiated output power could
mean higher energy absorption in tissues. However, a reduction in radiated
power due to mismatch or increased RF current on the device housing could also
lead to higher SAR. For devices that operate linearly, the measured SAR is
expected to be proportional to output power. When changes in radiated output
are used to estimate whether there is sufficient SAR margin to ensure
compliance for all the battery options, the output changes should be linearly
proportional to the measured SAR.
3.15 Device operating capabilities
3.15.1 For certain devices that are designed to
operate with a substantially low operating duty factor where constant peak
output power is neither supported by the hardware nor its battery, SAR
compliance should be evaluated at the highest operating duty factor expected
during normal use. If a device or its battery is not designed to maintain a
constant average output power, SAR should be evaluated with respect to the
highest exposure expected based on battery capacity. The measured SAR should
typically correspond to the average output power measured before and after the
SAR measurement. Testing a device beyond its intended maximum capability
and/or capacity may sometimes lead to unpredictable performance conditions that
could produce unacceptable test results. These types of test configurations
should not be used.
3.16 Device Operating Modes
3.16.1 If a portable transmitter has built‑in
test modes that can be used to evaluate the highest exposure during normal use,
SAR should be tested with these test modes. An unmodulated carrier is usually
used in AMPS mode test sequences. For TDMA mode, the test mode signal is
usually modulated by the time‑division duty factor. Testing TDMA devices
with an unmodulated CW signal and adjusting the SAR with a duty factor is not
recommended. The test mode signal for CDMA, direct‑sequence transmitters
should correspond to the full vocoder rate and maximum occupied bandwidth of
the device. Frequency hopping spread spectrum devices should be tested at
fixed frequencies corresponding to the high, middle and low frequency channels
to avoid field probe sampling time incompatibility issues. For devices that
operate with a transmission band less than 10 MHz, testing at the middle
channel is generally sufficient; otherwise, SAR should be tested at the high,
middle and low channels.
3.16.2 The following procedures must be used if the
difference between the highest output of a low output mode and the lowest
output of the highest output mode is more than 2 dB, otherwise, such low
output modes must be tested according to the normal Schedule 2 requirements.
The highest and lowest output of an operating mode must be determined with
respect to the output for high, middle and low frequency channel of each mode:
(a) test each of the lower output modes in the
configuration that resulted in the highest ten‑gram SAR in the mode with
the highest output; and
(b) test the lower output modes in the following
configurations when the ten‑gram SAR for the highest output mode of such
configurations are greater than 1.0 W/kg:
(i) the antenna position and channel
that produced the highest ten‑gram SAR in the Left Head Touch Position;
(ii) the antenna position and channel
that produced the highest ten‑gram SAR in the Left Head Tilt Position;
(iii) the antenna position and channel
that produced the highest ten‑gram SAR in the Right Head Touch Position;
(iv) the antenna position and channel
that produced the highest ten‑gram SAR in the Right Head Tilt Position.
(c) if the ten‑gram SAR measured for any
configuration in each of the lower output mode is greater than or equal to 85%
of that measured for the highest output mode, the normal Schedule 2
requirements should be used to complete the entire set of required tests for
such lower output mode(s).
3.17 Source‑Based Time Averaging
3.17.1 Duty factors related to device usage,
software programming or asynchronous operations that are not inherent to or
defined by the transmission protocols of the wireless network providing
services to the transmitter generally do not satisfy source‑based time
averaging requirements. However, for certain devices that are hardware limited
by design and are restricted to operate with a maximum RF duty factor, source‑based
time averaging may be considered. When source‑based time averaging is
required to demonstrate compliance, the device must be tested for SAR
compliance with the source‑based time‑averaging factor included in
the test signal. Devices operating with built‑in duty factors should not
be tested with CW equivalent signals to avoid over‑stressed operating
conditions, which could lead to unpredictable device performance and produce
unacceptable test results.
3.18 Recommended SAR Measurement Procedures
3.18.1 The SAR measurement protocol and test
procedures should be documented. The calibration traceability of field probes
and other supporting equipment should be attached to the SAR reports when such
information is requested. In each SAR report, the rationale for evaluating a
device with the specific test configurations to demonstrate compliance should
be clearly documented. The device operating conditions, such as output power
stability (drifts), performance variations (tolerances) or other physical,
mechanical and electrical variations, which could introduce unacceptable
changes in SAR results must be carefully characterized and considered in the
SAR evaluation to determine compliance. The test sample used in a SAR
evaluation must be substantially identical to production units to ensure the
test results are acceptable for demonstrating compliance.
3.18.2 For measurements using homogeneous phantoms,
the peak SAR locations are usually located at or near the surface of the
phantom. The measurement system must search for these peaks and determine the
highest SAR averaged over any ten gram of tissue medium in the shape of a cube
through additional measurements at one or more of these peak locations. Since
the field probe is calibrated at the geometric centre of its sensor elements,
where the measurement point is defined. The highest SAR typically occurring
near the surface of a homogeneous phantom cannot be measured by an electric
field probe with its sensors located 2‑4 mm behind the probe tip. These
SAR values must be computed by extrapolating the closest measured points to the
surface of the phantom for determining the highest ten‑gram averaged SAR.
3.18.3 The spatial resolution of a field probe is
related to a small volume surrounding the sensors within the probe. The size
of this measurement volume is probe dependent. The measured field values are
reduced at maximum field location and enhanced at minimum field locations
according to this averaging volume. To minimize this type of measurement
error, probes with a tip diameter larger than 8.0 mm should not be used (See Reference [6]). In steep gradient or non‑uniform
fields, higher isotropy error may be expected because the sensors are displaced
at the probe tip and from the probe axis. At boundaries of dielectric
interfaces, the tip of a probe must be immersed at least 2‑3 probe
diameters beyond the sensors to measure SAR correctly within the tissue
medium. This boundary effect happens at both the air‑to‑tissue and
tissue‑to‑phantom‑surface interface. To minimize such
measurement errors, it is also necessary to avoid making measurements with the
probe tip in direct contact with the phantom surface. For most probes, a
separation of at least half a probe diameter should be maintained between the
probe tip and the phantom surface to avoid requiring complex compensation
procedures to further reduce probe boundary‑effects errors.
3.19 Procedures to search for peak SAR
locations
3.19.1 Different extrapolation, interpolation and
integration algorithms have been used in existing measurement systems to
determine the highest ten‑gram SAR to show compliance. The following
procedures should be used to ensure the test results are acceptable.
3.19.2 To search for the peak SAR locations produced
by a test device in a head or body phantom, the electric field probe should be
scanned along the inside surface of the phantom filled with the required tissue
medium. A coarse resolution scan, also know as area scan, is used to determine
the approximate peak locations near the surface of the phantom, typically in an
area larger than that projected by the transmitter and its antenna. The
measurement should be performed at a fixed distance of 8.0 mm or less from the
inside surface of the phantom, with less than ±
1.0 mm variation. Laterally, the measurement points should provide a spatial
resolution that is sufficient for the interpolation algorithms used by the SAR
measurement system to identify the peak SAR locations to within half the linear
dimension of the 10‑gram cube (10.8 mm). This typically requires an area
scan resolution of 1‑2 cm. The SAR distribution may be plotted to verify
the peak SAR locations with respect to the near‑field exposure characteristics
of the transmitter. All peaks within 2.0 dB (63.1%) of the highest peak
identified by the interpolated data should be evaluated with a fine resolution
volume scan to determine the highest ten‑gram averaged SAR (See Reference
[6]). A SAR plot of the surface scan region with a sketch or picture of the
test device superimposed on the contours should be used to identify the peak
SAR locations.
3.19.3 If a peak SAR location is near the edge of a
scan region, within 10.8 mm for ten‑gram SAR (half the linear dimensions
of the cube), the area scan should be repeated with an expanded scanning
region. When SAR is measured along the side wall of a phantom or on curved
surfaces where the probe axis is not perpendicular to the phantom surface,
probe isotropy and probe boundary‑effects errors must be carefully
considered for making accurate measurements. For some measurement systems, the
E‑field probe may have been calibrated or compensated to measure SAR with
the probe axis oriented within ± 30°
from that normal to the phantom surface. If this is not the case, either the
phantom or the field probe should be re‑oriented to reduce the
measurement error.
3.20 Procedures for determining ten‑gram
averaged SAR
3.20.1 The fine resolution volume scan region, also
known as the zoom scan region, should be centred at the peak SAR locations
determined by the extrapolated data from the area scan measurements. The
number of measurement points required in a zoom scan to provide an accurate ten‑gram
averaged SAR is dependent on the field gradients at the peak SAR location. In
smooth gradients, the ten‑gram averaged SAR can be correctly predicted
with only a few measurement points. When steep field gradients exist, many
measurement points evenly distributed within the ten‑gram volume of the
tissue medium may be required to correctly predict the volume averaged SAR.
The zoom scan region should extend in each direction for at least 1.5 times the
linear dimensions of a ten‑gram cube of tissue from each peak. The zoom
scan spatial resolution should allow the interpolation algorithms used by the
SAR measurement system to compute SAR values on a 2 mm grid with less than 5%
error, which typically requires a zoom scan resolution of 5‑8 mm.
3.20.2 The peak field values near the surface of a
homogeneous phantom are usually not measurable because the sensors in a field
probe are located at 2‑4 mm behind the tip of the probe and the
measurement point is defined at the geometric centre of the sensors where the
calibration is defined. These SAR values must be computed by extrapolating the
closest measured points to the surface of the phantom to determine the highest
ten‑gram averaged SAR. The extrapolation algorithm must compensate for
the field attenuation based on a series of measurement points along a straight
line, extending from the phantom surface through the peak SAR location, in the
zoom scan region. The first two measurement points should be inside the ten‑gram
averaging volume. Both points should be less than 1.0 cm from the phantom and
liquid surface. The last measurement point should be outside the ten‑gram
averaging volume, typically within the zoom scan region. The SAR value for the
last measurement point should be less than 25% of the value measured for first
point closest to the phantom surface. The separation distance between adjacent
measurement points should be less than 5.0 mm. The extrapolation coefficients
should be determined with an appropriate curve‑fitting algorithm, such as
a 4th order polynomial least‑square fit. The same set of
coefficients should be used to extrapolate the SAR values that cannot be
measured within the zoom scan region (See Reference [6]). The extrapolated SAR
values should have the same spatial resolution as the zoom scan measurements.
3.20.3 The interpolated and extrapolated SAR values
from the zoom scan measurement are integrated in the shape of a ten‑gram
cube, for example, with a trapezoidal algorithm, to determine the highest
volume averaged SAR in the zoom scan region. SAR compliance is determined
according to the highest ten‑gram SAR measured for all the zoom scans
performed for each area scan. The error associated with the extrapolation,
interpolation and integration algorithms used in the area and zoom scans should
be analysed and included in the total measurement uncertainty.
3.21 Measurement Uncertainties
3.21.1 Measurement uncertainties are calculated
using the tolerances of the instrumentation used in the measurement, the
measurement setup variability, and the technique used to perform the SAR
evaluation. The overall uncertainty is calculated in part by identifying
uncertainties in the instrumentation chain used in performing each of the
procedures in the evaluation. Methods for evaluating and expressing
measurement uncertainties can be found in the NIST
Technical Note 1297 (TN1297), entitled ”Guidelines for Evaluating and
Expressing the Uncertainty of NIST Measurement Results” (See Reference [9]).
Another source of reference is the NIS 81 document, entitled “The Treatment of Uncertainty
in EMC Measurements,” published by the National Physical Laboratory of the
United Kingdom (See Reference [10]).
3.22 Types of Measurement Uncertainties
3.22.1 In general, the components of uncertainty may
be categorized according to the method used to evaluate them. The evaluation
of uncertainty by the statistical analysis of series of observations is termed
a “Type A” evaluation of uncertainty. The evaluation of uncertainty by
means other than the statistical analysis of series of observations is termed a
“Type B” evaluation of uncertainty. Each component of uncertainty,
however evaluated, is represented by an estimated standard deviation termed
“standard uncertainty”, which equals the positive square root of the estimated
variance. Details of Type A and Type B uncertainties are explained in NIST ‑
TN1297 (See Reference [9]).
3.22.2 The “combined standard uncertainty” of the
measurement result represents the estimated standard deviation of the result.
It is obtained by combining the individual standard uncertainties of both “Type
A” and “Type B” evaluations using the usual root‑sum‑squares method
of combining standard deviations by taking the positive square root of the
estimated variances.
3.22.3 “Expanded uncertainty” is a measure of uncertainty
that defines an interval about the measurement result within which the measured
value is confidently believed to lie. It is obtained by multiplying the
combined standard uncertainty by a “coverage factor”. Typically, the coverage
factor ranges from two to three. For a normal distribution, if the combined
standard uncertainty is a reliable estimate of the standard deviation, a
coverage factor of two defines an interval having a level of confidence of
approximately 95%. A coverage factor of three defines an interval having a
level of confidence greater than 99%.
3.22.4 A detail report of uncertainty should consist
of a complete list of the components specifying for each the method used to
obtain its numerical value. The uncertainty in the result of a measurement
generally consists of multiple components which may be grouped into either
“Type A” or “Type B” uncertainties. There is not always a simple
correspondence between the classification of categories “Type A” or “Type B”
evaluation of uncertainty and the previously used classification of random and
systematic uncertainties in earlier standards. The term “systematic
uncertainty” can be misleading and should be avoided.
3.23 Determining Total System Measurement
Uncertainty
3.23.1 SAR measurement uncertainties are the results
of errors due to system instrumentation, field probe response and calibration,
and the dielectric parameters of the tissue medium. Uncertainties due to
measurement procedures include test device placement, probe positioning procedures,
the extrapolation, interpolation and integration algorithms used to determine
the ten‑gram averaged SAR. The error components associated with the
total SAR measurement uncertainty for evaluating portable transmitters can be
grouped into four main categories ‑ assessment, source, device
positioning and phantom uncertainties. Assessment uncertainty is related to
the instrumentation and procedures used to assess the spatial peak SAR value in
a given SAR distribution for a given setup. Source uncertainty is related to
the test and operating parameters of the test device used in an evaluation that
produced the SAR distribution. Device positioning uncertainty is related to
the changes in SAR due to variations in device test position. Phantom uncertainty
describes the variation of a phantom model with respect to the desired model
and tissue dielectric parameters defined in the measurement protocol, such as
those recommended by SCC‑34/SC‑2.
3.23.2 The total SAR
measurement uncertainty stated in a SAR report quantifies the quality and
accuracy of the measurements with respect to the uncertainty of the
instrumentation and measurement techniques used for the evaluation. A summary
of the uncertainty analysis, including the uncertainty components considered
for the SAR measurement should be described in the test report to support
compliance. A statement of compliance indicating the maximum measured ten‑gram
averaged SAR with the corresponding expanded measurement uncertainty for each
operating mode and operating configuration tested for the device should be
included in the SAR report. Expanded uncertainty should be determined for a
confidence interval of 95% or higher, which corresponds to a “coverage factor”
of two or more. The measurement uncertainty of the SAR values must be less than
30%.
3.23.3 The measurement uncertainty components that
should be considered in a typical SAR evaluation, similar to those recommended
by the SCC‑34/SC‑2, are described below (See Appendix A and B). The
SAR equipment manufacturer may have evaluated some of these uncertainty
components according to specific measurement conditions, however, additional
analyses may be required for the uncertainty components that are dependent on
the operating conditions and test configurations of an individual test device.
Part 4 References
[1] Chou,
C., G. Chen, A. Guy and K. Luk, “Formulas for Preparing Phantom Muscle Tissue
at Various Radiofrequencies”, Bioelectromagnetics, 5, pp. 435‑441, 1984.
[2] Drossos,
A., V. Santomaa and N. Kuster, “The dependence of electromagnetic energy
absorption upon human head tissue composition in the frequency range of 300‑3000 MHz”,
IEEE Transactions on Microwave Theory and Techniques, vol. 48, no. 11, pp. 1988‑1995,
Nov 2000.
[3] Gabriel,
C., “Compilations of the Dielectric Properties of Body Tissues at RF and
Microwave Frequencies”, Brooks Air Force Technical Report AL/OE‑TR‑1996‑0037,
1996.
[4] Hartsgrove,
G., A. Kraszewski and A. Surowiec, “Simulated Biological Materials for
Electromagnetic Radiation Absorption Studies”, Bioelectromagnetics, 8, pp. 29‑36,
1987.
[5] Hill,
D., “A Waveguide Technique for the Calibration of Miniature Implantable
Electric Field Probes for Use in Microwave Bioeffect Studies”, IEEE
Transactions on Microwave Theory and Techniques, pp. 92‑99, Jan 1982.
[6] IEEE
Standards Coordinating Committee 34 on Product Performance Standards Relative
to the Safe Use of Electromagnetic Energy, “Draft Recommended Practice for
Determining the Spatial‑Peak Specific Absorption Rate (SAR) in the Human
Body Due to Wireless Communications Devices: Experimental Techniques”, P1528,
2001 (referred to as P1528 and IEEE SCC‑34/SC‑2 in
Schedule 2).
[7] Meier,
K., R. Kastle and T. Schmid, “Dosimetric Evaluation of Handheld Mobile
Communications Equipment with Known Precision”, IEICE Transactions, E80‑A(5),
pp.1‑8, May 1997.
[8] “Military
Handbook, Anthropometry of US Military Personnel”, DOD‑HDBK 743A,
February 1991.
[9] NIST
Technical Note 1297 (TN1297), “Guidelines for Evaluating and Expressing the
Uncertainty of NIST Measurement Results”, available at http://physics.nist.gov/Pubs/guidelines/TN1297/tn1297s.pdf. or by contacting NIST Calibration Program, Building 820,
Room 232, Gaithersburg, MD 20899‑0001 or by telephone at (301)‑975‑2002.
[10] NIS
81 document, “The Treatment of Uncertainty in EMC Measurements,” published by
the National Physical Laboratory of the United Kingdom, available by order from
United Kingdom Accreditation Services (UKAS), 21047 High Street Feltham,
Middlesex TW13 4UN, Tel: +44(0)20 8917 8556, Fax: +44(0)20 8197 8500/8499.
Appendix A Documenting the measurement uncertainty of
SAR evaluations
A. Assessment
Error (measurement system)
I.
Probe Calibration Error
1. Axial
Isotropy Error
2. Hemispherical
Isotropy Error
3. Spatial
Resolution Tolerance
4. Boundary‑effects
Error
5. Linearity
Error
6. Sensitivity
Error
7. Response
Time Error
8. Integration
Time Error
II. Readout
Electronics Error
III. Errors from RF
Ambient Conditions
IV. Probe Positioner
Calibration Error (absolute)
V. Probe
Positioning Error with respect to the Phantom Shell
VI. Errors from the
Extrapolation, Interpolation and Integration Algorithms
B. RF
Source Error (test device)
I.
Test Sample Output Power Drift Error
II. SAR
Variation due to Performance Tolerance of the Test Sample
III. SAR Variation due
to Tolerance of Production Units
C. Test
Device Positioning Error
I.
Test Sample Positioning Error
II. Device
Holder or Positioner Tolerance
D. Phantom
and Setup Errors (See Reference [6])
I.
Phantom Production Tolerance (shape and thickness)
II. Target
Liquid Conductivity Tolerance
III. Measured Liquid
Conductivity Error
IV. Target Liquid
Permittivity Tolerance
V. Measured
Liquid Permittivity Error
Appendix B Documenting the measurement uncertainty for
SAR system verification
A. Assessment
Error (measurement system)
I.
Probe Calibration Error
1. Axial
Isotropy Error
2. Hemispherical
Isotropy Error
3. Spatial
Resolution Tolerance
4. Boundary‑effects
Error
5. Linearity
Error
6. Sensitivity
Error
7. Response
Time Error
8. Integration
Time Error
II. Readout
Electronics Error
III. Errors from RF
Ambient Conditions
IV. Probe Positioner
Calibration Error (absolute)
V. Probe
Positioning Error with respect to the Phantom Shell
VI. Errors from the
Extrapolation, Interpolation and Integration Algorithms
B. RF
Source Error (typically a half‑wave dipole)
I.
Input Power Measurement Error
II. Output
Power Drift Error
C. RF
Source Positioning Error
I.
Separation Distance Error from the Source to the Tissue Medium
II. RF
Source (dipole) Holder or Positioner Tolerance
D. Phantom
and Setup Error (See Reference [6])
I.
Phantom Construction Tolerance (shape, dimensions and thickness)
II. Target
Liquid Conductivity Tolerance
III. Measured Liquid
Conductivity Error
IV. Target Liquid
Permittivity Tolerance
V. Measured
Liquid Permittivity Error