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IWR1843: About the Tx output power back-off for tx antennas

Part Number: IWR1843

Hi,

I am using txOutPower to decrease out power of Tx antennas, here is the related configuration:

channelCfg 15 1 0
adcCfg 2 1
adcbufCfg -1 0 1 1 1
profileCfg 0 77 916 7 57.14 30 0 70 1 256 5209 0 0 30
by setting txOutPower to 30, I see an obvisous drop of relative power.
Since maxium out power of Tx is about 12dB, the out power of Tx should be 12-30=-18dm. I am wondering if it means the Tx doesn't tranmit any signal? If so, why there are still two detected points in the figure.
Thanks.
  • Hello.

    The TX output power back-off code is 1) not in dB and 2) in decimal notation but from a converted hex number.  It is a 24 bit value, with every 8 bits representing the TX backoff for each transmitter.  For example, for a 10 dB back off for all 3 transmitters, the hex number would be 0A0A0A, which then converted to decimal is 657930.  You can do the same with 30 dB as well.  As a result, putting 30 as the parameter value in profileCfg is very close to 0 dB backoff, which is why you are still getting the detected points.

    Hope this helps,

    Santosh

  • Because I only use one Tx, so I think 30 is OK. 

    Set the back-off code to 1973790, which is 0x1E1E1E. The output is the same as the above figure.

    So, why there are still some detected points? Thanks.

  • Hello Jun.

    The power on that scale is relative so you won't see a major drop off even with a reduction in transmit power.  Also, why are you not trying to detect points?

    Sincerely,

    Santosh

  • OK. I just want to confirm that the transmit power is actually decreased.

    Thanks.