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WL1835MOD: Bluetooth LE default/max TX power

mickael9
Prodigy 140 points
Part Number: WL1835MOD


Hi,

I'm wondering, what are the default and maximum achievable output power levels for Bluetooth LE on the WL1835MOD ?

In the Vendor-Specific HCI Commands document, I've noticed the following lines about default ROM configuration (assuming VBat=3.3V)

#Set BT LE (BLE) HP Vectors Values (note the need to multiply the output power in dBm by '2'
Send_HCI_VS_DRPb_Set_Power_Vector 0xFD82, 9, -19.5 *2, -14.5 *2, -9.5 *2, -4.5 *2, 0.5 *2, 5.5 *2, 10.5 *2, 15.5 *2, 0x3F, 0x00FF

Send_HCI_VS_DRPb_Set_Class2_Single_Power 0xFD87, 5, 5, 5, 5, 5, 4, 5, 4, 4, 4

If my interpretation is correct, this would mean that by default, BLE Transmit power in HP mode is limited to level 5 which is 5.5 dBm, is that accurate?

The max value seems to be level 7 which is 15.5 dBm, is this achievable ?

Thanks

  • 0
    TI__Genius 12740 points

    Hi,

    The default power for BLE is limited by the FW. We cannot achieve the 15.5dBm output power here. Per our datasheet the BLE output power is limited to 7 dBm.

    Thanks,

    Riz

  • 0 in reply to Rizwan Murji
    Prodigy 140 points

    Hi,

    Thanks for your reply.

    I've looked at the datasheet again, and the 7 dBm figure seems to be the "typical" value, with an attached footnote: "Bluetooth low energy power is restricted to comply with the ETSI 10-dBm EIRP limit requirement". Should I understand that the typical value is 7dBm is the default one and it can be pushed to 10 dBm or that the 7 dBm value is the lowest that complies with 10-dBm EIRP ?

    Thanks again

  • 0 in reply to mickael9
    TI__Genius 12740 points

    Hi,

    In this case the 10-dBm power is referring to the EIRP number, which is the 7dBm + the gain of the antenna. Thus you need to ensure that the gain with antenna is less than 10dBm. For our modular certification we can support an peak antenna gain in the 2.4GHZ band of 3.2dBi. When you include the trace loss to the antenna we are below the 10-dBm mark.

    IF you are re-using the certification you want to ensure that you leave the default power at the 7dBm. IF you use a lower gain antenna, theoretically you can increase the power out of our device, but that will invalidate the certification as this can change the gain setting within the radio and the FCC requires you to retest in the case.

    Thanks,

    Riz