To determine whether your product needs Specific Absorption Rate (SAR) testing, there are a few items to consider.
First, is the device operated within 20cm (7.87”) of the head or body? If no, then SAR does not apply. If yes, then SAR does apply, but testing may be excluded based on the device’s output power.
The maximum conducted output power is the average conducted power at the antenna port plus any production tolerance. When calculating output power, keep in mind the device’s duty-cycle. For SAR, the on and off time-averaged power is to be considered. So if not already accounted for, the duty cycle factor may be applied directly to the output power.
To determine whether the output power is below the threshold for testing, it depends on where the device is being certified for. Here are some common jurisdictions:
The Federal Communications Commission (FCC) utilizes a formula to determine SAR test exclusion in KDB 447498 D01v05 Section 4.3. For separation distances of <50mm if the following equation results in <3.0 then test exclusion for 1g SAR applies: (Output power, mW) / (separation distance, mm) x (sqrt(freq), GHz). Use 5mm for separation distances <5mm.
Industry Canada stipulates the exclusion threshold in RSS-102. For 3kHz – 1GHz it is 200mW, for 1GHz – 2.2GHz it is 100mW, for 2.2GHz – 3GHz it is 20mW and for 3GHz – 6GHz it is 10mW. Note that per Industry Canada, output power is always the higher of conducted or equivalent isotropically radiated power (EIRP).
In the EU, the threshold is given in IEC/EN 62479:2010. A simple formula is used: Pmax = SARmax * m.
For each jurisdiction, if the devices output power is less than the threshold, SAR testing is not required. However, in most cases, a statement showing why it is excluded and how it still meets the requirements must be submitted.
This post is a good summary of SAR testing exclusions, but is not inclusive of all scenarios. Contact us to find out if your product is subject to SAR testing in these or other global markets.
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