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IWR6843: Question about the total transmit power when beamforming

EijiM
Prodigy 30 points
Part Number: IWR6843

Hi,

According to industrial toolbox "long range people detection" user guide, beamforming with 3Tx antennas

is available.

How much is the total transmit power when beamforming?

Is it three times as much as one of non-beamforming (16.8dBm) or maintained as 12dBm?

Thanks in advance.

Eiji

  • 0
    TI__Mastermind 25835 points

    Hello,

         Yes, If the the beams are aligned, using phase shifter then power will add up as you pointed out.

    Hence we are able to achieve long range people counting with this approach.

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Prodigy 30 points

    Hello,

    Thank you for your reply, but I'm afraid my question was not good. So let me correct it.

    In my knowledge, EIRP [dBm] is calculated as follows:

    EIRP = P + G + F = X + 10*log10(N) + G + F

    where P[dBm] is total transmit power, G [dBi] is antenna gain, F [dB] is array gain, X [dBm] is transmit power per antenna element, and N is the number of antenna element, respectively.

    I think you pointed out the gain by F or N. But my concern is P or X, not N or F.

    My question is "How much is X when IWR6843 beamforming? Is it changed from one of non-beamforming?"

    Sorry for my question being difficult to understand, but I hope for your answer.

    Thanks in advance.

    Eiji

  • 0 in reply to EijiM
    TI__Mastermind 25835 points

    Hello,

        Thank you for for clarifying in detail. While beamforming or non-beamforming modes in the above equation P or X will not change it would be maintained as 12dBm typical number (Unless there is Power back-off is applied). 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Prodigy 30 points

    Thank you for understanding my question. I understand transmit power per antenna X is maintained as 12dBm even when beamforming.

    If so, total transmit power and EIRP increase 4.77dB and 9.54 dB respectively because of coherent combining of 3Tx.

    Is my understanding correct?

    Sorry for asking many questions, but in my country not only EIRP but also transmit power is limited by the radio law and It is important for the practical use of IWR6843.

    I'd appreciate it if you could answer.

    Eiji

  • +1 in reply to EijiM
    TI__Mastermind 25835 points

    Hello,

       Yes, you are right, for the transmit power limit in your country, you could back-off the Tx power.

    When using the mmWave Visualizer and accompanying config file, the TX power back-off is specified by setting the TX backoff in the ProfileCFG parameter where each of the 8 bit values corresponds to TX1, TX2 and TX3 respectively.

    For example for a 6dB back-off on all TX channels, the TX power control word would be 0x060606 i.e. 394758 (use this decimal value). Here's the corresponding profileCfg command. profileCfg 0 62.00 30 10 69.72 394758 0 28.42 1 128 2180 0 0 24 This is defined in the mmwavelink html documentation. 

    You could refer to the SDK from the below location. 

    https://software-dl.ti.com/ra-processors/esd/MMWAVE-SDK/latest/index_FDS.html 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Prodigy 30 points

    Thank you for your reply. I will check Tx power control soon and I think this issue has been solved thanks to your kind answer.

  • 0 in reply to EijiM
    TI__Mastermind 25835 points

    Thank you for your confirmation. If you have any trouble in getting Tx power control please let us know. 

    Thanks and best regards,

    CHETHAN KUMAR Y.B.