How is SAR measured for radio communication products? What are the limits for SAR measurement

Bringing a new wireless communication device to market requires a list of requirements and regulations from the design stage to release. One of these requirements is related to consumer safety when using wireless devices. SAR is short for Specific Absorption Rate. This unit of measurement is used to determine the amount of radio frequency, RF energy absorbed by the human body. While products such as walkie-talkies and antennas that transmit radio communications have measurable SAR, cell phones are the most common source of RF energy.

SAR for Radio Communication Products

What are the limits for SAR measurement?

Electromagnetic fields, or EMF, have international guidelines on what is considered safe exposure to RF energy. The guidelines take into account potential device users of all ages to protect them from negative health effects. SAR is measured in Watts per kilogram, expressed as W/kg.

Internationally, general SAR limits are:

0.08 W/kg for whole body exposure

2 W/kg for local exposure to the head and body

4 W/kg for local exposure to the extremities

It is important to note that some countries may have their own limits. For example, the exposure limit for head and body in Canada and the United States is 1.6 W/kg.

How are SAR measurements captured?

To achieve the environment required for accurate SAR testing, a specialized lab setup is required. The test uses a container similar in shape and size to the average human body, filled with what is known as a tissue equivalent fluid.

The wireless communication device is then operated while placed against the container. The sensor probe monitors the RF energy at various locations within the head and body, with an external computer analyzing the data and recording the maximum SAR value experienced.

Are SAR levels constant during use?

The RF energy generated during lab testing is done at maximum power based on the certified power level of the device. For most consumer uses, SAR levels will be much lower than the resulting values, as most communication devices will use as little power as possible to maintain adequate voice quality.

In mobile phones, the highest SAR levels are found when a connection is established over a cellular network. Once a call begins, the device utilizes adaptive power control to reduce battery consumption and the RF energy transmitted.

SAR levels can be minimized by being closer to a cellular tower or base station that supports wireless communication. Users who are concerned about EMF and SAR levels can verify the maximum SAR of any device before purchasing.

Where can I find SAR testing services?

Luxshare Compliance Testing is one of the few laboratories in China that can measure all levels of SAR. Whether it is a commercial device or a consumer device ready for market, Compliance Testing can provide testing and regulatory guidance to prepare your product for certification.