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Original question:

AWR1642: Covert peakVal from linear to dB

AWR1642: What is the difference between peakVal of detectedObj and relative power of original mmwaveSDK?

Kris Lin
Intellectual 810 points
Part Number: AWR1642

Hi,

I changes the relative power from original mmwaveSDK to peakVal of detectedObj.

But these power values are not matched at the same detected object.

What is the difference between  peakVal of detectedObj  and relative power of original mmwaveSDK?

Thanks

------------

P: power

R: range

===============================================================

relative power of original mmwaveSDK (dB)

===============================================================

peakVal of detectedObj (dB)

===============================================================

  • 0
    TI__Guru*** 148154 points
    Hi,

    What are you trying to achieve with these changes?

    What application are you working on?

    Thank you
    Cesar
  • 0 in reply to Cesar
    Intellectual 810 points
    Hi Cesar,

    I would like to use the variable (peakVal of detectedObj) to implement the power of the detected object.
    But it seems difference between peakVal of detectedObj and relative power of original mmwaveSDK.

    I don't know which one is suitable for our application ?
    Do these two values of power have their own conditions of use?

    Thanks.
  • 0 in reply to Cesar
    Prodigy 115 points
    Hi Cesar,

    I also found the same problem during raw data processing.
    This peakVal of detectedObj was different from that of range profile,
    which makes me a bit confused...

    I would like to compare the received signal power of AWR1642 from a standard radar target (metal sphere) with theoretical value.
    Could you please give some instructions on the difference between two radar received signal powers?

    Thank you in advance.
    Kang
  • 0 in reply to LeonardEllis
    TI__Expert 4720 points

    Hi,

    If I understand your question correctly, you are trying to match two parameters (or at least understand what is different between them). The two parameters are detectedObj[iObj].peakVal  and relativePower from the visualizer graph? Am I correct?

    Regards

    Anil

  • 0 in reply to Anil Mani
    Prodigy 115 points
    Hi, Anil

    Yes, you're correct.
    Could you please give some instructions?

    Thank you in advance.

    Linick
  • 0 in reply to Linick
    TI__Expert 4720 points

    Hi Linick,

    The difference is primarily due to how the two parameters are computed in the Out-of-box demo. Other demos (like the SRR) may compute them differently. 

    'peakVal' (from the detected Obj structure) is computed in the function 'dss\dss_data_path.c :: MmwDemo_XYcalc()' and is simply the peak of the 'angle FFT' computed at a particular 'range-velocity' bin. Note that the angle-FFT is performed after the doppler-FFT and the range-FFT.

    'rangeProfile' is computed in the function 'dss\dss_data_path.c :: MmwDemo_interFrameProcessing()' and is 'zero velocity row' of the 'detection matrix' (in the code, this vector is called 'detMatrix'. The 'detection matrix' is compute after the range-FFT and doppler-FFTs (i.e. after 2D-processing). It is the non-coherent sum of the 2D-processing output across antennas.

    Regards

    Anil

  • 0 in reply to Anil Mani
    Prodigy 115 points
    Hi Anil,

    Thank you very much for the detailed instructions.
    It is clear to me now about the difference between these two parameters.
    You mentioned that the first one 'peakVal' is simply the peak of the 'angle FFT'.
    Does it have some physical meaning on its value?
    (e.g. reveals the sharpness of the peak in the result matrix after doppler-FFT and range-FFT )

    Best regards

    Linick
  • 0 in reply to Linick
    TI__Expert 4720 points

    Hi Linick,

    'peakVal' of a detected object denotes the 'relative' received power due to that detected object. You can use it to estimate the relative RCS of different targets  using the radar-equation. For e.g. if you have a corner-reflector of a known RCS, you can note down the 'peakVal' for that corner-reflector, and then estimate the RCS of other reflectors in a given scene - ( assuming the antenna gain is constant for the two measurements).

    You can also use the 'peakVal' to get an estimate of the 'true' received power i.e., you'd like to convert the peakValue to mW value (ie a power reading). In this case, you'd have to 'de-embed' a lot of parameters, including things like the FFT processing gain (over range-FFT, doppler-FFT, and angle-FFT), the rx-gain, the DFE-gain etc. Then,  with an estimate of the received power, you can apply the 'Radar Equation' and get an estimate of the RCS of a target. 

    Regards

    Anil

  • 0 in reply to Anil Mani
    Prodigy 115 points
    Hi Anil,

    Thank you so much for this detailed explanation.
    It is quite helpful to know that this 'peakVal' can be used to estimate the relative RCS of different targets.

    Best regards,

    Linick