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Original question:

IWR6843: Determining valid chirp parameters for SDK Demo

IWR6843: Chip Loops and frame periodicity in mmWave Studio sensor configuration tab

Cagri Tanriover
Intellectual 885 points
Part Number: IWR6843

Hi,

I need a quick clarification of "No of Chirp Loops" and "Periodicity (ms)" configuration parameters in mmWave Studio application. I am also providing a figure (as attached) to help with my question.

I have two different types of chirps as shown (red and black) Let's assume the duration of these chirps (i.e. T1 and T2) are the same. Each radar frame consists N such chirps as shown (N/2 black and N/2 red chirps in each radar frame). Each radar frame period ir Tf as shown. Tg is the time gap between consecutive frames.

My first set of questions are as follows:

1 - Is "No of Chirp Loops" = N ?

2 - Is Tf = "Periodicity (ms)"?

3 - Does the tool calculate the time gap between frames (Tg) automatically?

My second set of questions are related to the "Active-Ramp Duty Cycle" and the "Duty Cycle" parameters that are automatically calculated in mmWave Studio. I'm including the famous chirp reference diagram below to assist.

My questions are:

1 - Is "Duty Cycle" = (Tf - Tg) / Tf ? (based on the first diagram above)

2 - Is "Active-Ramp Duty Cycle" = T(tot) / Tf where T(tot) is the total time of all the "ADC Sample Time" (as indicated in orange below) for each chirp inside a frame?

Thank you for your help.

Regards,

Cagri

  • 0
    TI__Mastermind 23655 points

    Hello

    For 1st of questions - the answer depends on how you post process them. Typically for coherency the processing is done for identical chirps so that SNR can be improved  so in that case N/2 would be your chirp count and black and red ones would be separately processed and different cubes.

    We will get back with more details.

    To help users with chirp design we have a sensing estimator tool that takes in sensing requirements and creates FMCW parameters compliant with device requirements.    https://dev.ti.com/gallery/view/mmwave/mmWaveSensingEstimator/ 

    Hope that helps you with Chirp design without having to worry about FMCW equaltions.

    Thank you,

    Vaibhav

  • 0
    TI__Mastermind 36725 points

    HI, Cagri:

    Please see my answers inline.

    1 - Is "No of Chirp Loops" = N ?

    From the figure, in this frame, you have two type of chirps, (red and black), so you should define two chirp, chirp index 0 and chirp index1, and the number of chirp loop should be N/2 in your case.

    2 - Is Tf = "Periodicity (ms)"?

    Yes, Tf is the frame period. 

    3 - Does the tool calculate the time gap between frames (Tg) automatically?

    Yes, Tg will be calculated automatically. 

    Regarding your second set of questions 

    1 - Is "Duty Cycle" = (Tf - Tg) / Tf ? (based on the first diagram above)

    Yes.

    2 - Is "Active-Ramp Duty Cycle" = T(tot) / Tf where T(tot) is the total time of all the "ADC Sample Time" (as indicated in orange below) for each chirp inside a frame?

    For each chirp, the total duration is the chirp idle time plus the chirp ramp time.  The active ramp duty cycle only accounts for the ramp time, not the idle time.  But the ramp time includes the adc start time, ADC sample time and excess time. So ADC sample time is only part of the total ramp time. 

    Best,

    Zigang

  • 0 in reply to Vaibhav Mahimkar
    Intellectual 885 points

    Thanks Vaibhav. After thinking about this question in a bit more detail, treating identical chirps as part of the same processing chain makes a lot of sense. This is the route I am planning to take in my implementation.

    Regards,

    Cagri