Meaning
Power levels or separation distances below which a device does not require formal specific absorption rate testing. These limits are set by regulatory agencies to reduce the burden on manufacturers of very low-power transmitters. Falling below the SAR exemption thresholds allows a product to enter the market without a full laboratory evaluation of energy deposition.
Calculation Method
Engineers determine the maximum possible output power including antenna gain and manufacturing tolerances. If this value is lower than the SAR exemption thresholds for the intended use case, the device is deemed compliant by design. This calculation depends on the operating frequency and the distance to the human body.
Design Efficiency
Avoiding the expense and time of full laboratory testing is a major goal for wearable electronics. Efficiency is required. Working within the SAR exemption thresholds requires a careful balance between the link budget and the transmit power settings.
If the power must be increased to maintain a stable connection, the device may lose its exempt status. This decision impacts the final cost and the speed of the product launch.
Regulatory Variation
Different international bodies maintain their own sets of power limits and distance rules. While a device might meet the SAR exemption thresholds in one region, it may require full testing in another. Staying updated on these changing rules is necessary for global product distribution.
