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AWR1642: What is the Chirp repition period and Active frame mentioned in the mmwave Sensing estimator

Santhana Raj
Expert 1765 points
Part Number: AWR1642

Hi,

I used mmwave Sensing estimator to figure out the sensor/signal parameters.  I used the following parameters.

My questions is: What does the terms "chirp repetition period" and "Active Frame time" mean.

I thought the chirp repetition period is the time period of each chirp. But that value of 131.5us doesn't match with the other values like (Idle time+ramp time = 65.75us). Even if we assume that the idle time of 7us is minimum value and actually the value is larger, to meet the chirp repetition period, this value doesn't match with the active frame time. Active frame time is 8.42ms, and for 53 chirps, the chirp rept period has to be 151.74us.

There seems to be a mismatch. Either I am missing some time factor in-between or my understanding of chirps timing is wrong. Kindly help me.

I actually want to know the inter chirp time and inter frame time.

  • 0
    TI__Guru 58035 points
    Hello Santhana,
    Chirp repetition period is the time between two similar chirps. In the above example there would be one chirp with TX1 and other with TX2 , so the repetition between two TX1 chirps would be 2*(idle time + ramp end time).

    regards,
    Vivek
  • 0 in reply to Vivek Dham
    Expert 1765 points

    Thank You for pointing out my silly mistake. It is evident now.

    About Active frame time, for a chirp repetition time of 131.50us and 53 chirps, the minimum frame repetition time can be 6969.5us or 6.97 ms. The active frame time is 8.42ms as per the estimator. I assume that in includes the inter frame time also. Am I correct?

    If that is the case, how to arrive at the extra 1450.5us. What parameters control it? What value I have to change in my inputs to increase or decrease this?

  • 0 in reply to Santhana Raj
    TI__Guru 58035 points
    Hello Santhana,
    You are right, the active frame time should have been 6.97msec. let me double check on that.
    The inter frame time (the extra time between the frames) is controlled by the "frame periodicity" parameter in the frame config API. For example if you set the frame periodicity as 10msec then the inter frame time would be set to 10-6.97 = 3.03 msec.

    regards,
    vivek