SAR test reduction procedure for module

RE: SAR test reduction procedure for module or device with combined Bluetooth and RLAN technology operating in the 2402MHz to 2483.5MHz frequency band.

Currently, more and more devices and modules incorporate a combination of Bluetooth and RLAN technology (e.g. IEEE802.11b, g and/or n) that are co-located.  Bluetooth and RLAN operating at 2.4 GHz often use the same power amplifier and antenna system; however one operating at lower power than the other. Industry Canada has developed a test reduction procedure in order to reduce the number of SAR measurements that would normally be required for radio apparatus employing both these technologies.

The following test reduction procedure may be used to reduce the total number of SAR measurements performed for Bluetooth. The procedure must be applied separately for head, body worn/mounted and hot spot test configurations.

With respect to devices that require simultaneous transmission SAR evaluations, the reported SAR results acquired using the test reduction procedure described herein can be used for determining the SAR values for simultaneous transmission scenarios. For the test configurations that do not require a SAR evaluation based on the following test reductions or on the power exemption limit thresholds stated in RSS-102 Issue 5, a SAR value of 0.4 W/kg or an estimate SAR value based on the ratio of the Bluetooth power level and the power exemption limitFootnote 1 can be used to determine the standalone SAR value for Bluetooth.

Bluetooth Test Reduction Procedure

The procedure can only be applied if the following requirements are met:

  1. The same RF amplifier stage is used for Wi-Fi and Bluetooth
  2. The same antenna is used for Wi-Fi and Bluetooth
  3. The time-averaged output power for Bluetooth is at least 2 dB below the output power of Wi-Fi
  4. The same SAR measurement system (probe, phantom, liquid, and electronics) is used for all modes.

Test Reduction Procedure:

  1. Based on the reported SAR results for Wi-Fi in the stated frequency range (taking into consideration the tune-up tolerance), determine the test configuration (test position) that resulted in the worst case reported SAR for Wi-Fi.
  2. If the maximum time-averaged output power measurements performed for Bluetooth are within 1/4dB for the low, mid, and high frequency channels, perform SAR measurements for Bluetooth using the same test configuration which resulted in the worst case reported SAR for Wi-Fi on the Bluetooth channel closest to the same tested Wi-Fi channel. Otherwise, measure SAR on the channel with the highest time-averaged output power measured for Bluetooth. For devices with multiple Bluetooth operating modes, SAR testing for Bluetooth shall be conducted on the mode with the lowest order modulation as long as the measured time-averaged output power (including tune-up tolerance) of the higher order modulations is within 1/4dB of the lowest order modulation operating mode. However, if this is not the case, the mode of operation with the highest time-average output power including tune-up tolerance must be used to conduct SAR evaluations.
  3. If the reported SAR for Bluetooth is <=0.8W/Kg (including tune-up tolerance), no further testing is required for Bluetooth. If the reported SAR for Bluetooth is >0.8W/Kg, measure SAR for all remaining default Bluetooth test channels (e.g. the low and high frequency channels if the mid channel was previously assessed).
  4. To determine additional SAR test requirements for the remaining test configurations when the reported SAR for Bluetooth is >0.8W/Kg, estimate the SAR for Bluetooth as follows for the next highest SAR test configuration (based on the Wi-Fi test configurations):
    1. Determine the SAR ratio (Rsar) based on the worst case reported SAR for Wi-Fi (Wi-Fi sar1) and Bluetooth (BTsar1) as follows using the previously determined reported SAR results for the worst case test configuration;
      1. Rsar = BTsar1 / Wi-Fi sar1

    2. Calculate the estimated SAR for Bluetooth (BTsar2) for the next test configuration which resulted in the next highest Report SAR results for Wi-Fi (Wi-Fi sar2) as follows;
      1. BTsar2 = Wi-Fi sar2 x Rsar 
  5. If the estimated SAR for Bluetooth in the next highest test configuration is <=0.8W/Kg, no further testing is required for Bluetooth. If the estimated SAR is >0.8W/Kg, measure SAR for Bluetooth using steps 1 to 4 above until the Reported SAR in step 3 or the estimated SAR in step 4 is <=0.8W/Kg for the next highest test configuration.