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AWR1642BOOST: What is the order of doppler FFT at 'fftOut2D' in SDK mmw 1642 demo ?

JinHyeong Kim
Intellectual 460 points
Part Number: AWR1642BOOST

Hi, 

I am trying to transmit all range doppler output of virtual antennas through lvds channel.

As far as I know, the variable fftOut2D at MmwDemo_DSS_DataPathObj_t structure contains 2D fft output of one virtual antennas for one range bin.

If there are 16 doppler bins,  does fftOut2D[0] mean zero doppler or minus velocity(towards radar). If so, what is the order of doppler bins?

Is is for -maximum velocity~+maximum velocity? 

Thanks 

Regards

Jinhyeong

  • 0
    TI__Guru*** 149044 points

    Hi

    The chirps are processed in the order they are Tx.

    First processed doppler  is for the first range bin from each chirp.

    Thank you

    Cesar

  • 0 in reply to Cesar
    Intellectual 460 points
    Hi,
    What i mean is that what is the order of velocity of the 2dFFT output.
    If fftOut2D[0] may mean zero velocity, what does fftOut2D[1], fftOut2D[3].... means?
    When I plot those result in matlab, it does not seem to be in order.

    Thank you
    Jinhyeong
  • 0 in reply to JinHyeong Kim
    TI__Expert 5235 points

    Look at the doppler index as a 2s complement signed number e.g if number of doppler bins is 16, then indices 0..15 of the 2D FFT output in signed 2s complement will look like 0,1,..7,8,...15 => 0,1,...7,-8,...,-1. The positive numbers mean target is moving away from the sensor (phase is increasing from one chirp to next in time) and negative means target moving towards the sensor (phase is decreasing from one chirp to next in time).