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IWR1443: Scaling of Magnitudes

Michael Linden
Intellectual 375 points
Part Number: IWR1443

  I'm working with code based on the High Accuracy Lab and would like to get a better understanding of the magnitude values that are being generated. For a certain reflection, dataPathObj.rangeProcStats.maxValue shows a value of about 230000. If I look at dataPathObj.rangeProcStats.maxIndex and use that to find the appropriate element in the Range Profile (MMW_HWA_CFAR_OUT = gMmwHwaMemBuf[2]) I see a value of about 14500. This is clearly the correct element in the Range Profile because it is the largest value in the array. These two magnitudes are from the same reflection, but I don't understand how they are related (scaling) and what their maximum values are. How are they related and what are their maximum values?

  Thanks! -Michael

  • 0
    TI__Guru 50240 points

    Hi Michael

    It appears it is simply a scaling factor obtained exclusively from the 1D FFT.

    Your ratio of 230,000 to 14,500 is about 16.

    I just ran a spot test and found a ratio of 42,000 to 2500, so about 17.

    The scaling factor comes from the visualizer where the 1D FFT output datastream is decoded and then plotted as the range profile.

    Regards,

    AG

  • 0 in reply to Akash Gondalia
    Intellectual 375 points

    Morning Akash:

      For now I'm going to have to assume a value of 17. However, use of the word "about" concerns me. While this information is not available in any documents, I would think that someone there knows exactly what the ratio is.

      I also need to convert these values into a percentage where 100% is the maximum value. I have not been able to find a maximum value in the documentation. Do you know what the maximum values are?

      Thanks, Michael

  • 0 in reply to Michael Linden
    TI__Guru 50240 points

    Hi Michael

    The  1D FFT data so is merely used to determine the range bin for which to perform zoom FFT on, so it is of less concern to us. Are you using the 1D FFT in addition to high accuracy measurement in your application?

    Regards,

    AG

  • 0 in reply to Akash Gondalia
    Intellectual 375 points

    Hi Akash:

      Yes. My application also requires presentation of the radar scene (amplitude versus distance). This "Range Profile" data will be the basis of of that graph. However, I need to understand the maximum amplitude of those values in order to scale the amplitude portion of that graph. In addition to that, I need to understand the maximum amplitude presented by the results of the zoom FFT (like dataPathObj.rangeProcStats.maxValue), and how that amplitude relates to the amplitudes in the Range Profile. In reality, knowing any two of these three items should be adequate. Does this make sense?

      Thanks, Michael