SARBACKOFF Probleme

IoT Modules WP Series
1

I am encountering an issue with the AT!SARBACKOFF command. My goal is to reduce the TX power of the GSM. I am attempting to apply a SARBACKOFF using the following commands:

bashCopy code

cat /dev/ttyAT &
AT!ENTERCND=\"A710\"
AT!DAFTMACT
AT!SARBACKOFF=3,1,1,1,0,9" 
AT!DASBAND=10
AT!DASCHAN=62
AT!DAGSTXFRAME=0,1,3200,0" 
AT!DASTXON

I have tried all SARBACKOFF combinations and applied them to all slots, but the output power remains at 32dB

2

Hi @bilal.kassem,

Are you looking to perform the GSM RF Transmission Path Test? Please follow the instructions in section 12.4 UMTS (WCDMA/GSM) RF Transmission Path Test on page 160 of the following document: AirPrime - WP76xx - Product Technical Specification
Furthermore, which specific WP are you using? Please use the module with the latest firmware from the source page to perform the Transmission Path Test.

Thanks,

3

Thank you for your response,

I am using a WP7702 with firmware R14.1. We have a product containing the WP7702, and our goal is to certify this product. However, during certification, we noticed that the 2G bands at 850 MHz and 900 MHz have a harmonic with a power greater than -30dB, which poses a problem.

We have tried to find a solution to eliminate this harmonic without success. Therefore, we want to use SARBACKOFF to limit the GSM power because if the power of the initial signal decreases, the power of the harmonic should also decrease. However, the AT!SARBACKOFF command is not working.

I have tried all combinations of SARBACKOFF with all slots and states without success. When I use AT!SARBACKOFF? to check if my command has been taken into account, I see that my SAR limit has indeed been limited.

However, when I launch the test and measure with a spectrum analyzer, I observe a power of 32dB, knowing that my SAR limit is set to 23 dB.

4

Hi @bilal.kassem,

Because the AT!SARBACKOFF command is not combined within the 12.4 GPRS/EDGE RF Transmission Path Test.
Therefore, in this case, it’s best to send an email to technical support at support@sierrawireless.com for further assistance.

Thanks,