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AWR1642: Limitation of No of Doppler bins

Santhana Raj
Expert 1765 points
Part Number: AWR1642

Hi,

I would like to set the number of chirps to less than 16. lets say 8 for a specific use case of mine.

From frame config doxy file, I know that no of frames should be a value greater than 16. I went through the code of mmw demo, and see that this restriction is only because of the limitation in my Doppler windowing.

In my modified code, I have modified this condition check, and I am able to run with 8 chirps.

My question is, Is there any other limitation either from hardware side or from software side for limiting the number of chirps to less than 16?? other than the obvious reduction in velocity resolution.

Thanks in advance,

Santhana Raj

  • 0
    TI__Guru 50240 points
    Hello Santhana,

    I've asked an AWR member to look at this for you. Someone should have an answer for you shortly.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    TI__Expert 4720 points
    Hi Santhana,

    There are no limitations in the hardware w.r.t to the number of chirps. However, the software and in particular the FFT routines supplied on the DSP expect at least 16 samples as input. You can see the issue in the DSP FFT routine file (C:\ti\dsplib_c64Px_3_4_0_0\packages\ti\dsplib\src\DSP_fft32x32\c64P\DSP_fft32x32_i.c) at line 456. That being said, it may work for 16 samples. There are three ways to proceed.

    1. You can check if the FFT output is correct for a given input, which may be possible depending on the optimizations optimizations the compiler attempts.
    2. You can zero-pad the FFT input (i.e. add an extra 8 zeros to the input array).
    3. You can write a simple function that performs an in-place discrete time fourier transform on 8 samples.

    Regards
    Anil
  • 0 in reply to Anil Mani
    Expert 1765 points
    Hi Anil,

    Thank you for the clarification.
    We are thinking to go ahead with option 3.