Most of us would find it very difficult to live without our smartphones. We either do not know (or choose to conveniently forget!) that these hand-held mini computers emit electromagnetic (EM) radiation in the form of radio waves. This EM radiation has to be measured for compliance with regulatory and other requirements before any market launch.
A mobile phone has both transmitter and receiver sections. When a mobile device is operating, it emits radio waves that consist of radio frequency (RF) energy, a form of electromagnetic radiation moving at the speed of light. It works by transmitting radio wave signals to, and receiving these from, nearby base stations.
Fears that these RF fields could affect our health have prompted legislators to set limits. Many countries around the world have adopted guidelines set by the International Commission for Non-Ionizing Radiation Protection (ICNIRP). These guidelines refer to a specific absorption rate (SAR), a measure of the rate at which EM is absorbed by the human body, when exposed to radio waves. This happens when we use a mobile phone, for example.
In order to test the SAR of mobile devices in an accurate and reproducible way, proper measurement tools and methods need to be used in a standardized way. One of the core competencies of the IEC is to standardize measurement tools and techniques in order for electrical and electronic devices and systems to be used and perform safely. This work benefits manufacturers, testing laboratories, regulators and the general public.
IEC set up a technical committee to standardize the methods for the assessment of electric, magnetic and EM fields associated with human exposure. Extremely active, IEC TC 106 has just published a new standard which establishes a novel measurement procedure for the assessment of the SAR of human exposure to RF fields from wireless communication devices.
State-of-the-art measurement technology
The standard breaks new ground because it provides requirements for fast SAR measurement systems, using a vector-probe array solution. This system determines the 3D EM field, by using a 3D reconstruction algorithm in a phantom, a sort of mannequin or physical model of the human body. “This type of testing would take around five weeks using traditional measurement methods. Vector-based measurement enables manufacturers to carry it out in less than half a day, which saves a considerable amount of time and money as well”, says Jafar Keshvari, who leads the project team that produced the standard.
53 members from 14 different countries took part in the development work. “Industry users, SAR equipment manufacturers, academia and, very importantly, regulators were involved. Jafar managed to include all these different viewpoints and form a very collaborative group. The regulator input was crucial and we think the standard will be widely adopted internationally, in the US, Europe and Asia and in some cases serve as a blueprint for legislation”, adds Mike Wood, Chair of IEC TC 106.
Collaboration with the Institute of Electrical and Electronics Engineers (IEEE) was also a fundamental asset. “It really is a joint standard. IEC worked with the organization’s International Committee for Electromagnetic Safety. Our project team also had great support from IEC TC 106 Secretary Matthias Maier”, Keshvari says.
Looking towards the future, Keshvari expects to extend the measurement range to reach lower and higher frequencies as well as develop the technology to measure power density, which is being looked at for 5G systems. “IEC TC 106 includes a dynamic group of engineers, many of which are young engineers and professionals. They give a lot of their time to prepare these foundational standards”, says Wood. They are foundational because they pave the way for new technologies such as 5G and the IoT to be used as routinely and as safely as possible.