"Specific Absorption Rate measurements for Mobile phones"

Synopsis of Presentation

Specific Absorption Rate ( SAR) compliance is mandatory for mobile phones and similar handheld devices. SAR is a RF dosimetric quantity and is defined as the rate at which RF energy is absorbed per unit mass of biological tissue. The absorption and distribution of 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 very 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. Dosimetric 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. One of the major difficulties encountered in dosimetric compliance measurements, is the location of the site of maximum SAR for a given device given that the SAR must be measured inside a complex 3 dimensional phantom filled with tissue simulating liquid.

This paper gives an overview of SAR measurement procedures and equipment necessary to carry out precision SAR measurements. The Choice Hands Free Kit Study will be presented and it will be shown that the use of Hands Free Kits with mobile phones greatly reduce RF radiation to the head. A detailed analysis of the controversial UK (Which?) protocol will also be presented, highlighting the major flaws in that study. A comparison of the European, FCC, ACA and proposed ARPANSA SAR limits will also be provided, highlighting the major factors that influence the SAR values of mobile phones when measured with the different standards.

Chris Zombolas
Technical Director
EMC Technologies Pty Ltd
chris@emctech.com.au

Chris Zombolas is Technical Director and founder of EMC Technologies Pty Ltd, an independent Australian based company with EMC/EMI, EMR, SAR, Safety and Radiocoms accredited laboratories in Melbourne, Sydney, Adelaide and Auckland (NZ). He has 29 years electronics experience in the defence and commercial electronics industries, with the last 21 years concentrated in Electromagnetics areas. He is a NATA signatory for testing to various Australian and international Electromagnetic Compatibility, Electromagnetic Radiation and Specific Absorption Rate standards. He has carried out numerous SAR tests and studies on mobile phones, hands free kits and other handheld and body worn transmitting devices.

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