In recent years, wireless technology has dramatically improved to meet the needs of the digital era. Users are often continuously connected to some form of wireless device. Data consumption has increased (and is increasing!) which is creating the need for more frequency bands and higher bandwidth to accommodate the data needs of the average consumer. The number of devices used in close proximity, and even worn on the body, is increasing.
Most portable devices will be used within 20cm of the body, head, ankle or wrist. At this proximity, the user is exposed to energy emitted by radio waves — how wireless devices communicate. Exposure to these fields can be of concern.
Check out this article on the UL Blog about “Biological Tissue Absorption from Wireless Devices”.
What is SAR Testing?
When you use a wireless product, it emits radio waves. Some of that energy is absorbed by the user when the device is placed close to the body, which happens often. You place electronics near your ear, a wearable on your wrist or laptop near your legs, etc. We put that device under test to help ensure the end-user is protected from electromagnetic radiation, or in other words, the way that wireless devices communicate.
Is this a form of radiation?
There are different levels of radiation. Some, like ionizing radiation, can have nasty effects to the body. The type we’re testing for is called radiofrequency radiation (RF radiation). It’s the same as the energy used in a microwave oven, but at a lower power.
What are the Effects of RF Radiation?
Even low power RF fields can have effects on tissue when they are in such close proximity to the body. We help ensure devices meet the required government regulations. These requirements minimize the amount of radiation the body can absorb, helping devices operate a safe level.
How are you testing for it?
In this demonstration, we will show how we measure the specific absorption rate of RF energy. We have two different types of simulators. — this yellow one simulates the human head, and the other red one simulates the human body. Inside, we have a liquid that is designed to exhibit the electrical properties of organs, muscles and bone.
We place the device, in this case a phone, under the head or body simulator and place a call at maximum power. Then, the robotic arm probes into the liquid to measure the RF field of different areas. After about 35-45 minutes, we can create a model of the RF field within the body. This is then evaluated to ensure the body is not absorbing unsafe levels of RF energy that exceed the regulations. The number of scans depends upon the supported tech (Wi-Fi, GSM, LTE, etc.).
How do I know that my phone or device has gone through this testing?
Luckily, this testing is required by almost every nation around the world. In the U.S., the limits and test methods are specified by the FCC.