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Range FFT processing details

Michelle Liu
Genius 11405 points


In general my understanding is that the Range FFT runs inline with every chirp, so e.g. for 128 chirps we have 128 Range FFTs.
When we enter the Intra frame processing time, how do we determine now range out of the 128 Range FFTs?
Is there a particular algorithm running for this?
What is the "processing gain" for this?

  • 0
    TI__Genius 11405 points

    If your goal is distance only, you could average the FFTs to get some averaging gain. The processing gain is not important in determining distance. You will calculate range resolution and count the bin which has the highest magnitude.

    There are several different methods to post process the 128 Chirp FFT results. In this weblink reference, flylib.com/.../, Understanding Digital Signal Processing (2nd Edition) R. G. Lyons there is:incoherent averaging - Equation 11-19

    FFT processing gain arises from the nature of FFT and it increases as the number of bins inceases. or use equation FFT gain = 10*log(Nfft/2) where Nfft is FFT bin size.There is an additional processing gain from the combination of multiple RX antennas. This is an incoherent processing gain as we sum powers across the antennas before detection.