SAR
RFI: At the cutting edge of SAR testing
What is SAR?
SAR is defined as “a measurement of the time derivative of the incremental electromagnetic energy absorbed by an incremental mass contained in a volume of given mass density”. If a part of the human body was exposed to electromagnetic energy (from technologies such as GSM, DECT, 3G, LTE, WiFi, Bluetooth®,TETRA, etc) then SAR would be used to quantify the level of energy absorbed, typically by a given mass in a given volume. Typically SAR is measured in mW/g or W/kg.
RFI's 10 years of experience and innovation
SAR testing forms part of the Radio & Telecommunications Terminal Equipment (R&TTE) EC directive to demonstrate compliance with health requirements. To market a product with radio frequency transmitter(s) or a products that influences a devices’ RF performance, and which is used in close proximity to the human body, there are requirements that must be satisfied and SAR is one of them. As the use of mobile technology spreads into newer territories, many countries around the world are increasingly concerned with the health and safety impact of using RF transmitters in close proximity to the human body. Europe, North America, Central America, South America, Australia and Asia all have SAR standards which products now have to meet.
Measurement of SAR
RFI has considerable experience in performing customised research and developing SAR technology for third parties, in particular where non-standard test phantoms may be required and testing at frequencies which require new human body simulation fluids. Over recent years RFI has contributed to both commercial and government research projects for RF Dosimetry.
RFI has many years experience in SAR evaluations, delivering certification testing for devices requiring CE, FCC, IC and ARPANSA approvals. Due to our comprehensive theoretical knowledge and practical experience, we are able to provide technical advice, project management and conformance testing to ensure your products meet essential requirements based on your intended market. Working on technical committees we guarantee that we are up-to-date with the latest international standards and drafts, as well as being kept abreast of the regular changes in the FCC Knowledge Database and Permit-But-Ask procedures and requirements.
What is involved in SAR product compliance?
Typically a test plan is generated to ensure that for a given test sample all technologies, antenna configurations and operating modes are considered. SAR measurements require the use of liquids that simulate human tissue and has appropriate electrical and dielectric properties (specifically, permittivity and conductivity). The varying composition of parts of the human body (e.g. head, torso, legs) means that each part has unique dielectric properties which are also dependent on the frequency of the exposure source. Liquids are mixed specifically for each frequency band and body part. This means that there are different liquids used for simulating Head and Body when performing SAR tests. Additionally the test requires the use of a phantom / mannequin called a “SAM” (Specific Anthropomorphic Mannequin). The SAM is shaped according to the SAR standards and filled with the appropriate body simulation liquid, comprising of a shaped head section and flat body section as indicated below. This allows a device to be positioned against the Head and Body on the flat section, as required.
The transmitting device under test is mounted against the SAM under the phantom, and placed into a test mode where it transmits at maximum power and appropriate duty factor. RFI uses the “industry standard” SPEAG DASY4 system to perform SAR measurements. An E-field probe mounted and controlled by a high precision robot, penetrates the SAR liquid and scans the entire surface of the device under test, plotting “hot spots” (i.e. regions of highest RF energy). When a hot spot is found a “volume cube” is than placed over the point with the highest field and the average SAR is measured within this volume.
Frequency Range we cover:
RFI’s SAR system can be use for compliance and research & development work and the DASY system has probes that operate from 10MHz up to 6GHz. With radio devices having multiple technologies that can operate simultaneously, the system is designed to assess each frequency component individually. Almost all device manufacturers utilise the SAR system to show compliance with health standards. RFI is accredited under ISO 17025: 2005 to perform SAR measurement in the following frequency bands and example technologies:
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Frequency Band (MHz)
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Example Technology
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350 to 550
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TETRA, GSM450, PMR, ISM, FM
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650 to 1000
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American and European GSM850 / EGSM900, UMTS, LTE
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1650 to 2250
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American and European DCS / PCS, UMTS FDD/TDD, DECT
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2350 to 2700
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WLAN 802.11b/g, LTE, ZigBee™, Bluetooth®
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3600 to 3700
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WiMAX
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5100 to 5900
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WLAN 802.11a/n
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RFI is able to test at other frequencies and technologies on request. The DASY system can also be used in free space measurements to view field distribution.
SAR measurement and regulatory work for the global market
Governments around the world support international committees in order to ensure standards are developed and published to maintain health and safety. Europe and Australia use human exposure limits which are independent from those mandated by the United States and Canada. The SAR limits for Europe and Australia are averaged over a 10g mass volume, while the United Stated, Canada and parts of Asia use limits which are referenced to 1g average mass volume. Due to these differences, tests performed to European and Australian standards are not readily accepted by the United Stated, Canada and parts of Asia. Another anomalous contributing factor is the fact that frequency bands at which, for example, GSM devices operate varies across these countries.
Tests performed to either the European (CE) or American (FCC) test standards (IEC/IEEC) are accepted in majority of countries around the world, although in some cases minor changes may be required. RFI performs SAR testing to all of these standards, ensuring our customers’ product(s) are release without delays and eliminating the possibility of a product recall from the global market.
RFI routinely offers SAR and RF exposure measurements to the following standards:
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Standard
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Description
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EN 50360 / EN 62209-1
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CE – Mobile phones and other hand-held devices (head only)
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IEC/EN 62209-2
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CE - international standard for a broader range of body-worn devices (final draft version)
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EN 62311
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CE – product not defined in the above standards
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EN 50383 / EN 50385
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CE – base stations
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FCC OET Bulletin 65 Supplement C
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FCC – covers all kinds of SAR measurements
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IEEE 1528-2003
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Mobile phones and other hand-held devices (head only)
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ACA 2003 / ARPANSA
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Australian SAR standard
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In cases were there is uncertainly over which standard should be applied for a given technology, our regulatory team can help you. We offer consultancy on global approvals and certification which allows customers to market their products. We have extensive knowledge in certification work and our TCB team is always welling to assist. Talk to us to find out how we can help you take your product to market in the shortest possible time and ensure regulatory compliance.
See our UKAS accreditation to see a full list of standards. Contact us to discuss your requirements.
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