TEC and the department of telecommunications have strict rules on SAR measurements and it is mandatory that any mobile phone imported to India should be tested for SAR.
Benoit Derat, Ph. D., CEO and president, ART-Fi and Rahul Gautam, head-market development, electromagnetics compatibility (EMC), Rohde & Schwarz spoke to Sneha Ambastha, Electronics Bazaar to share their views about the market requirement for SAR testing and it’s benefits.
Q. What is Specific Absorption Rate?
A. Specific Absorption Rate (SAR) is basically the amount of electromagnetic field produced by mobile phones. It is very important that we control SAR. Mobile manufacturers have to measure and show this value on their device in compliance with exposure limits to human body. They can only sell devices fit complies with SAR test requirements.
Q. What is the difference between EMC/EMI testing and SAR testing?
A.The basic electromagnetic compatibility or electromagnetic interference (EMI/EMC) testing is performed for interference between two machines. This is to ensure that radiation emitted by one machine should not disturb other machines. But when we do SAR testing, it only looks at the effect on humans due to radiation.
Q. How has SAR testing evolved?
A. With the development of wireless technology, using traditional and slow methods has become difficult. This is because with development of technologies like Long Term Evolution (LTE), the number of tests per device in order to perform the SAR compliance is extremely large. Traditional compliance testing of a smartphone would be across four or five weeks free shifts, but with the machine we developed it could be finished in one week.
Q. How does newer SAR testing devices work?
A. The probes here are totally computerised and fixed, enclosed inside the head or the body of the mannequins on the machine. The device itself doesn’t move but is placed against the mannequin to simulate various conditions of mobile phone usage. So you fix the device in one position and the probes inside the mannequin are activated electronically to perform a complete scan below the surface of the device. The scan captures the energy that is transferred from the device into the biological tissue simulating material. Then you apply algorithms to obtain the field everywhere you want to have it.
Q. What are the specialties of this new SAR machine?
A. The former technology would measure only the magnitude of the electric field, but we measure both magnitude and phase. We can apply algorithms based on physical science to reconstruct the field in a complete volume from only a few points using equations, which is not possible with traditional systems. The test time is also reduced due to multiple probes that are connected electronically. They apply calculation algorithms in a fast computer to get the results delivered in seconds.
Q. What is the international situation on SAR testing?
A. In Europe, people more or less ignore it although there are obligations for displaying it. The World Health organisation (WHO) supports the fact that there are some limits established by some expert committees that should not be exceeded in order to make sure that the human health and safety is not at risk. That’s why it is very important that we continue monitoring these types of values through equipment that can make those measurements.
Q. What is the critical SAR value, beyond which it is considered harmful?
A. The compliance limit varies across regions. India has chosen to align to the US limit, which is on one gram average SAR. This means SAR average on 1 gram of tissue is limited to 1.6W/kg. In other countries of the world limits are defined differently. For example in Europe we apply a 10gm SAR averaging and the limit is 2W/kg. Scientists wanted to have a very cautious approach putting a very low limit to make sure that we never get very close from the edge of the cliff. As of now the limits prove to be safe by a large margin.
The higher the SAR rating, the better the range / reception on the phone.
The only measured effect that non-ionizing radio frequency electromagnetic energy from a phone has is a tiny fraction of a degree heating of soft tissue. Yet people are OK walking in sunlight, using a heating pad, bathing in warm water, or even warning their hands by a fire – all of which have an enormously greater soft tissue heating impact.
So use SAR in the only meaningful manner: to choose a device with a better signal.
Even today, there is absolutely no HARD EVIDENCE on any Ill effects caused by SAR. Not a single patient or effect can be attributed to SAR and can be proven. It is an outcome of some scientific experiments.