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Original question:

IWR1642: CW Doppler Radar

IWR6843: Possible CW radar implementation on IWR6843

Jacob Miszczak
Prodigy 70 points
Part Number: IWR6843
Other Parts Discussed in Thread: IWR1642,

Hi,

I read a related forum(linked below) and was wondering if there where any other possible implications for my implementation of a Continuous Wave radar for high-velocity targets. I know in the previous forum it was stated that there was a continuous wave mode but only for testing purposes and won't work for low Doppler shift frequencies. But if the doppler shift frequency was larger then 350KHz(corner frequency of HPF2) would there be any other implications in implementing a CW into one of my subframes?

Thanks,

Jacob

TI forum:IWR1642 CW Doppler Radar

https://e2e.ti.com/support/sensors/f/1023/t/755307

  • 0
    TI__Mastermind 25835 points

    Jacob,

       Wanted to understand your application for this question. Could you please elaborate more on need of CW radar implementation, how does it brings advantage over FMCW signal.

    As you mentioned indeed HPF filters are the limiting factors for the velocity estimation. A Doppler shift of 350KHz – corresponds to a relative velocity of about  850m/s. So the velocities need to be quite high. 

    With the conventional FMCW chirping method is superior compared to CW Doppler radar, You could get both Range and Doppler information (even very low speed) in one go. With the advent of hardware accelerators for FFT and embedded DSP inside the mmWave sensor cost of the signal processing is negligible as compared to classical CW Doppler processing. Also with the Hardware accelerator FFT processing (which is very efficient and fast)  is abstracted out with simple API commands, Hence it would offer lot more advantage over classical CW Doppler radars. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Prodigy 70 points

    Hi Chethan,

    My application would be tracking bullets which would mean the need to capture high-velocity low RCS projectiles. The reason for the possible implementation of CW with our design is the need to track objects at very high speed >500m/s, from what I've seen this speed would be ambiguous If I tried to track with the IWR6843. With a possible insertion of a CW Dwell, I could track the unambitious velocity followed by subframes of chirps to track the range. 

    Thanks,

    Jacob

  • 0 in reply to Jacob Miszczak
    TI__Mastermind 25835 points

    Jacob,

       Thank you for providing details on your application. 

    You could still use the fast FMCW to unambiguously estimate these high velocities, You would get the aliased velocity of the bullet using the range-Doppler FFT in a single frame. The un-aliased velocity can be got by looking at the range change across multiple frames. Since the speed is high – the change in range bins would be large enough to measure the unambiguous velocity. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Prodigy 70 points

    CHETHAN KUMAR,

    Thank you for the timely response I will look at your idea and see if it could work for my implementation.

    Thanks,

    Jacob