A large and growing number of devices now use wireless radio transmitters to send and receive information. Statistics from the ITU, the leading United Nations agency for information and communication technology, show that global mobile-cellular subscriptions will reach more than seven billion by the end of 2015.
With this widespread use of mobile technology, and the growing popularity of wearable technology, consumers and governments are increasingly aware of the potential health risks of radio frequency (RF) energy emissions. As a result, strict regulations apply when these devices come into contact with the human body – particularly in the European Union (EU), the United States, Canada, Australia, Japan and India.
What is SAR?
SAR (specific absorption rate) is a measurement of how much electromagnetic radiation is absorbed by body tissue whilst using a wireless device - the higher the SAR, the more radiation is absorbed. SAR is usually averaged either over the whole body, or over a small sample volume (typically 1g or 10g of tissue).
The concept of SAR has been around for many years and RF safety concerns are not a new development. Most consumers are aware that a microwave oven can heat tissue (food) by using RF power, and it is this heating affect from mobile device that causes the most concern from an RF safety point of view. SAR limits are therefore set to protect end users from wireless devices if these are used near to the user’s head or body.
SAR test standards:
Country / Area
ACMA EMR Standard, 2003
Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) Standard, 2002
The Australian SAR standard is set by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), and regulated by the Australian Communications and Media Authority (ACMA). The requirements are set out in the Radio Communications Act 1992 and the ACMA Electromagnetic Radiation - Human Exposure (ACMA EMR) Standard 2003.
These regulations cover all common radio services, including AM and FM radio, police, fire and ambulance services, mobile phones and mobile phone base stations. Before a mobile device can be sold, the manufacturer must provide test results to the ACMA.
Health Canada and Industry Canada are responsible for maintaining radiofrequency exposure guidelines, better known as Safety Code 6, to ensure that all equipment manufactured, imported, sold or leased in Canada meets the stringent radiofrequency exposure requirements. Industry Canada’s Radio Standards Specification (RSS) 102, Radio Frequency Exposure Compliance of Radiocommunication Apparatus (All Frequency Bands), sets out the requirements and measurement techniques that must be used to evaluate RF exposure compliance of wireless devices designed to be used within the vicinity of the human body. Health Canada updated the Safety Code 6 in March 2015, providing a much more stringent limit for RF Evaluation of Mobile devices, as well as more stringent SAR test exclusion criteria.
In Europe, manufacturers that want to place a wireless device onto the European market must meet the requirements of the Radio and Telecommunications Terminal Equipment Directive (R&TTE). Manufacturers of wireless devices, which use radio frequency energy, must therefore comply.
The R&TTE Directive will be superseded by the Radio Equipment Directive (RED) in June 2016. The essential requirements of the RED are largely identical to those of the R&TTE Directive. However, there is an important change in this new legislation for the health & safety aspects, changing “intended use” to "reasonably foreseeable conditions". The consequence of this is that body-worn devices will need to be tested in contact with the container of the fluids that mimic the body, rather than at a recommended distance from it. This will make compliance with the SAR requirements more difficult to achieve.
The Federal Communications Commission (FCC) has adopted limits for safe exposure to radiofrequency (RF) energy. The FCC requires wireless device manufacturers to ensure that their devices comply with the objective limits for safe exposure. The FCC Rule Part 2.1093 contains requirements for portable use devices, as do the FCC’s series of SAR Knowledge Database Publications. On 16th March 2015, the FCC released a final version of KDB 248227 D01 V02, which provides comprehensive guidance on SAR measurements for devices incorporating 802.11 a/b/g/n/ac radios. Only the latest published procedures can be used when submitting devices for approval.
What is SAR testing?
TÜV SÜD is one of the earliest established independent SAR laboratories. We work with surveillance authorities across the world, which pull products from retailers’ shelves, so that we can test them to verify the SAR levels declared by the manufacturers.
SAR testing measures the heating effect on human tissue, to determine if a wireless communications device meets the requirements for RF exposure. A probe is positioned at various points within a phantom head or body, which is filled with tissue simulant fluid that matches the dielectric characteristics of the human body.
For head SAR testing, a 2D/area scan is carried out to show the location of highest SAR (hotspot) against the phantom. A Zoom Scan/ 3D scan is then carried out to find the “maximum averaged SAR” for that position. With testing using the head phantom, the highest SAR is not always adjacent to the antenna as the antenna may be beyond that phantom, but SAR is present where the device comes in contact with the phantom. With body testing using the flat phantom, the SAR measurement (hotspot) is normally adjacent to the antenna in the device.
Although the declared SAR is determined at the highest operational power level, this represents a worst case scenario as in normal operation the actual SAR level of the device, while operating, could be well below the maximum value. This is because mobile devices are designed to operate at multiple power levels, so as to use only the power required to communicate effectively with the network. This means that the closer the end user is to the base station, the lower the power output of the device and vice versa.
However, the SAR value is heavily dependent on the location of the antenna in the device, coupled with the RF output power. It is also influenced by the distance used during testing between the device and the fluid that simulates the body: the shorter the distance, the higher the SAR value measured. It is the manufacturer’s responsibility to ensure that samples used to measure SAR levels at the compliance phase of development match the final product that will go into large-scale production, before they are placed for sale on the market.
What should you be doing?
Equipment manufacturers are legally required to declare the SAR rating of their products in many countries. In some markets, this information must appear on the outer packaging. Non-compliance may result in large fines. In the event that surveillance authorities question your SAR rating, acquiring a test report from an independent third-party laboratory such as TÜV SÜD proves that you have acted with due diligence. Ultimately, this enhances your reputation as a trustworthy manufacturer that considers the safety of end users.
Mobile devices from many well-known and ‘trusted’ brands are also likely to carry a Notified Body number after the CE logo. This shows that the product has been independently verified by the Notified Body. For example, the Notified Body number of TÜV SÜD BABT, one of the world’s leading telecommunications certification bodies, is 0168.
For well-known brands, reputation is vital and compliance with SAR regulations is therefore paramount to them. However, the requirement in the new EU RED legislation to carry out measurements in worst case mode, rather than in the way recommended by the manufacturer, will make it much harder for body-worn devices to avoid breaching the maximum permitted SAR values. Furthermore, with the substantial growth in mobile technologies and the emergence of many new manufacturers, lesser known brands may struggle to comply without assistance.
How can TÜV SÜD help you?
TÜV SÜD’s accredited laboratories for SAR testing are respected worldwide, and our SAR test experts provide comprehensive advice and guidance on all of the requirements for your products to be sold in your intended markets worldwide. By conducting pre-compliance or investigation testing ahead of formal testing, we identify any potential issues at an early stage, and we can also provide the final certification for you.
Our SAR testing services include:
SAR initial product check – carried out on a number of spot frequencies this gives a general SAR level indication. We provide advice and estimate the time and budget required for formal SAR testing.
Customised SAR testing following manufacturer/ industry specifications – this covers the growing number of radio devices being placed into environments that are not traditionally covered by standard measurement techniques, but which still need to comply with health requirements.
Formal SAR testing – this is executed to published standards and legislation, supported by a full test report that can be used as evidence of compliance with the specific market’s requirements.