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AWR1642: Chirp parameters based on mmwave sensing estimator

Andy Yin
Genius 9380 points
Part Number: AWR1642

Hi,

Using the mmwave sensing estimator to get the chirp configuration as below figure, it reminded the chirp period is too long, but based on my calculation all the parameters are correct, would u pls help let me know why it reminded such error, any limitation?

Andy

  • 0
    TI__Guru*** 149044 points
    Can you please share the calculation?

    Thank you
    Cesar
  • 0 in reply to Cesar
    TI__Genius 9380 points
    Cesar,
    I referred to the SWRA553 to calculate the d_max, d_res, v_max and v_res, all can match, and beat frequency in the above map is 4.84MHz which is less than the IF BW 5MHz. I cannot understand why it reports such error. Need your help to clarify, greatly thanks.
    Andy
  • 0 in reply to Andy Yin
    TI__Genius 9380 points
    Anyone can follow the issue, u can input the parameters in the estimator to reproduce the issue, I cannot understand why it reports chirp time is too long?
  • 0 in reply to Andy Yin
    TI__Guru*** 149044 points
    Yes,

    We will try it.

    Sorry for the delay

    Thank you
    cesar
  • 0 in reply to Cesar
    TI__Mastermind 24955 points
    Andy,

    If you decrease the number of TX antennas down to 1, then you can leave all of your other parameters the same and you will not receive any errors.

    Regards,
    Kyle
  • 0 in reply to Kyle Cousino
    TI__Genius 9380 points
    Hi Kyle,
    Yes u r right the error disappear if decrease the number of Tx antennas to 1. But i cannot understand why it reports such error if number of Tx antennas is 2, would u pls help let me know why? We need to know the root cause to get the optimal RF parameters.
    Thanks.
    Andy
  • 0 in reply to Andy Yin
    TI__Mastermind 24955 points
    Andy,

    We are looking into this issue further. The reason this particular chirp configuration throws an error is related to the maximum velocity resolution that is specified by the user. In this case, you input a maximum velocity of 100 km/h. However, based on the chirp configuration that is generated by the tool, the maximum velocity is calculated to be 99.72. If you were to simply change the maximum velocity from 100 to 99, all errors would go away. Additionally, changing the frequency range from 76-77 to 77-81 removes all the errors, but this is due to the change in the carrier frequency. This is detailed more below.

    Here is how we arrive at the maximum velocity of 99.72 km/h.

    Maximum velocity = c / (4*fc*1000*Tr)
    where
    c = speed of light
    fc = carrier frequency
    Tr = chirp repetition period

    The carrier frequency is 76.14 GHz since the carrier frequency is defined by:
    fc = starting frequency + (ADC start time*Ramp Slope) + Bandwidth

    As a result, the carrier frequency is 76.14 GHz

    The chirp repetition period is defined by the ramp end time plus the idle time

    Tr = (Ramp end time + idle time) * Number of Tx antennas
    Tr = (15.8 + 2) * 2
    Tr = 35.60 us

    Using all of these calculated values, we arrive at a maximum velocity of

    Maximum velocity = (2.998*10^8 m/s) / (4 * 76.14 GHz * 1000 * 35.60 us)
    Maximum velocity = 27.7 m/s
    Maximum velocity = 99.72 km/h

    So it appears that the chirp configuration you are trying to implement should work as expected. The maximum range for a typically detected object will be around 58 meters.

    Please let me know if you have any additional questions.

    Regards,
    Kyle