When measuring the SAR due to a mobile phone the phone is placed against a representation of a human head in a talk position. The SAR value is then measured at the location that has the highest absorption rate in the entire head, which in the case of a mobile phone is often as close to the phone’s antenna as possible.
Measurements are made for different positions on both sides of the head and at different frequencies representing the frequency bands at which the device can transmit.
Depending on the size and capabilities of the phone, additional testing may also be required to represent usage of the device while placed close to the user’s body and/or extremities. Various governments have defined maximum SAR levels for RF energy emitted by mobile devices. SAR values are heavily dependent on the size of the averaging volume.
The guidelines created a measure of the rate that body tissue absorbs radiation during cell phone use called the specific absorption rate (SAR). The SAR for cell phone radiation was set at a maximum of 1.6 watts of energy absorbed per kilogram of body weight.