SAR testing (Specific Absorption Rate test) is used to measure the rate at which radio frequency (RF) energy released by wireless devices (such as mobile phones, tablets, etc.) is absorbed by human tissue during use. The SAR value is an indicator of RF energy absorption, usually measured in watts per kilogram (W/kg). This test is to ensure that wireless communication devices do not exceed the RF energy exposure limits set by international safety standards when operating at maximum power. SAR testing mainly focuses on the following two aspects: Local SAR: Measures the maximum RF energy absorption in specific parts of the body (such as the head or wrist). This is especially important for mobile phones and other wireless devices used close to the body. Whole-body SAR: Calculates the average energy absorption rate of the entire body during device operation. Different countries and regions have different SAR limits. For example, the United States Federal Communications Commission (FCC) stipulates that the SAR value of mobile phones must not exceed 1.6W/kg (measured based on 1 gram of tissue), while Europe allows a maximum SAR value of 2W/kg (measured based on 10 grams of tissue). SAR testing is usually conducted in certified laboratories using special testing equipment and liquid that simulates human tissue (commonly referred to as SAR phantom liquid). During the test, the device is placed in a position similar to that of the human body and operated at different frequencies and power levels to simulate actual usage conditions. Then, a specialized probe measures the RF energy absorption in the phantom liquid to determine the SAR value.