Wednesday, July 9, 2008

What is SAR Value?

Specific Absorption Rate (SAR) is a measure of the maximum rate at which radio frequency (RF) energy is absorbed by the body when exposed to radio-frequency electromagnetic field. It is used for exposure to fields between 100kHz and 10 GHz.

The SAR value will depend heavily on the geometry of the part of the body that is exposed to the RF energy, and on the exact location and geometry of the source of the RF energy. Thus tests must be made with each specific source, such as a mobile phone model, and at the intended position of use. The value cited for a specific model is then the maximum level measured in the body part studied.

The most common use is in relation to mobile phones, and here the mobile phone is placed at the head in a talk position. The SAR value measured is then value measured in the place that has the highest absorption rate in the entire head, which for a mobile phone often is as close to the phone as possible. Various governments have defined safety limits for exposure to RF energy produced by mobile devices that mainly exposes the head or a limb for the RF energy:

  • United States: the FCC requires that phones sold have a SAR level at or below 1.6 watts per kilogram (W/kg) taken over a volume of 1 gram of tissue.
  • European Union: the SAR limit is 2 W/kg, averaged over ten grams of tissue.

For whole body exposure there is a limit of 0,08 Watt/kg averaged over the whole body.

For more informations:

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