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Original question:

IWR1642: Pure Doppler radar

IWR1642: CW Doppler Radar

Katsuhiro Miyamoto
Expert 1430 points
Part Number: IWR1642
Other Parts Discussed in Thread: IWR6843, AWR1243, MMWAVE-STUDIO

Hello,

Is xWR1642, IWR6843, AWR1243 and xWR1443 possible to operate as CW Doppler Radar?

Fd=2v/λ, where Fd=Doppler shift frequency, v=relative velocity and λ=wave length.
E.g. In case that v=30m/s (108km/h) and λ=3.8cm (f=79GHz), Fd=15.8kHz.

The lowest HPF1/2 corner frequency is 175kHz/350kHz, that means Fd cannot pass through HPF1/2. As I confirmed in another thread before, HPF1/2 cannot be bypassed by HW design.
https://e2e.ti.com/support/sensors/f/1023/t/694977

Is it really possible to operate in CW Doppler Rader mode?

Best Regards,
Katsuhiro

  • 0
    TI__Mastermind 30405 points
    Katsu-san,

    Let me check on this with our Systems folks and get back to you in a day or two. Thanks for your patience.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    TI__Mastermind 30405 points
    Hi Katsu-san,

    Thanks for your patience. We do not support CW Doppler Radar. While our device has a CW mode which you can configure in MMWAVE-STUDIO, it is meant for testing purposes.

    However, our mmWave Sensors already provide Doppler i.e. Velocity information natively along-with Range and Angle of Arrival so you always get the Doppler information if that's the goal of the application.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    Expert 1430 points
    Hi Nitin,

    Thanks a lot for confirming.
    Can you explain some more detail of the reason why CW Doppler Radar is not supported please?
    Is it because of HPF corner frequency as I suggested, or other reason? It would be appreciated if you would elaborate it technically.

    Best Regards,
    Katsuhiro
  • 0 in reply to Katsuhiro Miyamoto
    TI__Mastermind 30405 points
    Katsu-san,

    I'm still looking into this and expect to have a response for you tomorrow. Thank for your patience.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    TI__Mastermind 30405 points

    Hi Katsu-san,

    Your understanding is spot-on. CW Doppler Radar is not supported because the Doppler shift for typical moving targets such as humans and vehicles will be too small to pass through the HPF. With small chirp times, TI FMCW can natively measure velocities up to 150-200 Kmph and the max velocity can be extended up to 4-5 times the native max using high level processing on the DSP (VMax extension using tracking). 

    The HPF provides isolation between TX and RX and also helps in dealing with near field reflections (bumper effect) and it cannot be bypassed as you confirmed in the other thread.

    Please mark the thread resolved if your query was answered otherwise get back if you have more questions on this topic.

    Regards

    -Nitin    

  • 0 in reply to Nitin Sakhuja
    Expert 1430 points
    Hi Nitin,

    Sorry for late reply because of taking New Year's holiday.
    Thanks a lot for detailed explanation. The reason why CW Doppler Radar is not supported becomes quite clear to me.

    Best Regards,
    Katsuhiro