Why test for SAR?
Electromagnetic radiation (EMR), also known as non-ionising radiation,
is generated by virtually all devices that transmit RF energy. It is
known that exposure of the human body to high levels of EMR may lead to
adverse health effects. To ensure the protection of personnel in the
workplace and to protect members of the general public, the Australian
Communications Authority (ACA) and other government bodies around the
world such as the FCC and the European Commission, have mandated new
regulatory frameworks which set compliance requirements for RF
transmitting devices. Owners and operators of Radio and
Telecommunications equipment, manufacturers and importers will need to
establish compliance with the EMR standards which in many cases require
SAR evaluation. In the USA, the FCC sets SAR limits and test
methods for SAR evaluations. In Australia, compliance
requirements are prescribed in the ACA EMR Standard 2003. Most
other countries have similar requirements.
 The first phase of the ACA EMR framework commenced on the 31 January
1999. The current scope of the ACA EMR standard 2003 includes
mobile phones and mobile phone base stations such as AMPS, GSM,
CDMA, DECT,
CT2/CT3, PHS, spread spectrum devices, WLAN laptops, tablet PCs,
PDAs etc.
The ACA and FCC scope now includes devices used at the head and devices
used near any other part of the body. These devices must be evaluated
against the ACA or FCC mandatory human exposure standard, which sets basic
restrictions for the Specific Absorption Rate (SAR) of RF energy.
The absorption and distribution of RF electromagnetic energy in the
body are very complex phenomena that depend on the mass, shape and size of
the body, the orientation of the body with respect to the field vectors
and the electrical properties of both the body and the environment.
Accurate measurements of the electromagnetic field in the extreme near
field of transmitters is therefore a difficult task. The complexity
of the field distributions places great demands on measurement probes with
respect to spherical isotropy, linear response, spatial resolution,
minimal field disturbances and boundary effects. SAR evaluations of
mobile telecommunications equipment (MTE) present the most restrictive
specifications where tight margins are set with respect to the maximum
permitted exposure, based on spatially averaged peak absorption. The
measurement uncertainty must not exceed 30% ( 1 dB!!)
Read more about SAR testing of Mobile/Cell phones
SAR journal articles by Chris
Zombolas
Compliance Engineering
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