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AWR1843: Target Induced Range/Doppler Noise Spread in 2D FFT of AWR1843

Shuo_Li
Prodigy 140 points
Part Number: AWR1843

Hello,

Our sensor is using AWR1843 Radar chip, and we notice some target-dependent noise from the 2D FFT plot.
The first and second figure is the FFT of testing in the empty chamber and there is no apparent noise after range bin 120 (120 bin is the end of the chamber room). However, after putting 1 corner reflector (around 90 bin) into the detection area, the 2D FFT becomes noisy as shown in the third figure. Moreover, these noises are located in different Doppler bins as circled in the fourth figure. Two strong noises are on the side of the target, and the other three are in the place that has already exceed the chamber range (ghost targets).
We have been looking this from an SI/PI standpoint and also from a potential front-end saturation standpoint. It would be good to get some guidance from TI engineers and see if others are seeing this same issue.

Looking forward to your replay.

-Simon

  • 0
    TI__Guru 69960 points

    Hello Simon,

    Could you confirm if addition peaks are multiple of the original peak?

    And which application you are using for this experiment, mmw demo??

     

    Regards,

    Jitendra

  • 0 in reply to Jitendra Gupta
    Prodigy 140 points

    Hi Jitendra,

    For the noises that I circled on the figure, only the last spike is approximately 3 times the range bin of the target. But I don't think the noises are multiple of the original peak as they are all detected with Doppler speed (all physical targets in the test are stationary).

    The 2D FFT plot is generated by following mmw demo.

    Thanks,

    Simon

  • 0 in reply to Shuo_Li
    TI__Expert 4720 points

    Hi Simon, 

    Could you share the chirp parameters? 

    I suspect that the reflections you see are a combination of

    1) 'reflections of reflections of reflections' (i.e double reflections) 

    1) low level spurs, 

    2) phase noise induced noise-floor. 

    Regards

    Anil

  • 0 in reply to Anil Mani
    Prodigy 140 points

    Hello Anil,

    The chirp slope is 72MHz/us, and the receiver gain is set to 30. The ADC sampling rate is 12MHz with 512 samples. 

    I can understand the double reflection creating spike at twice the range, but could you give me some detailed explanation of the other 2 noises? Since we don't observe those noises in the clean environment (no target chamber), such spikes are brought by the corner reflector, not the board itself.

    Thanks,

    Simon