The SAR (Specific Absorption Rate) test is the ratio of the electromagnetic energy absorbed by the human body when the human body is exposed to radio frequency (RF) electromagnetic field energy. The unit is defined as the energy absorbed per kilogram of mass (W/kg).

And why is it necessary to test SAR, because all kinds of organs in the human body are consuming medium, so the electromagnetic field in the body will generate electric current, which will absorb and dissipate electromagnetic energy. The purpose of this test is to ensure the electromagnetic wave of the wireless radio frequency product, causing excessive harm to the human body.

At present, the two major international telecommunications regulators, CE and FCC, have clear requirements for electromagnetic radiation. CE's electromagnetic radiation regulations are derived from the International Electrotechnical Commission (IEC). The FCC's electromagnetic radiation regulations are derived from the American Institute of Electrical and Electronics Engineers ( IEEE).

There are two methods for electromagnetic radiation, one for SAR testing and one for maximum permissible exposure (MPE) evaluation. Which method is used depends on the distance, maximum power, and usage status of the product.

According to the distance of use of the product, it is divided into the following two categories:

1. Portable device - transmission equipment with distance ≤ 20cm from the human body, SAR evaluation is required;

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2. Mobile device (Mobile) - transmission equipment with a distance of ≥ 20cm from the human body, requires MPE evaluation.