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AWR1843: Elapsing time between two consecutive chirp sample

Jonathan Navor
Genius 9475 points
Part Number: AWR1843


Hi Experts,

Good day! I need your assistance. 

I would like to ask something related to radar AWR1843. I'm doing research of this radar and I have something out of my knowledge. I'm trying to plot the Range-Doppler map once I have obtained the RawData from the radar. To do so, I need to apply an FFT transform but when I try to plot it the scale is not good, I would really like to ask what is the elapsing time between two consecutive chirp samples.

Reformulated question.
I have collected data with the AWR1843 radar, and with an external Matlab code, I would like to be able to process it. When making the Range-Doppler map I made the FFT of the samples put in matrix form. Throughout the chirps, which in my case are 128, in order to carry out the speed scale, I must resort to radar theory to convert frequency into speed, when doing so, the dimension does not give me the correct one.

To calculate the frequency I use the recurrence of f=1/N*fs sine N is the number of chirps and fs the sampling frequency. The doubt is that I don't know how often the samples of the chirps are collected. In the same chirp, the sampling frequency is the one defined in the parameters, but in the case of each chirp... How often are the chirps collected? That is, what is the sampling frequency with respect to the chirps?

Thank you in advance.

Best regards,

Jonathan

  • 0
    TI__Mastermind 20605 points

    Hi Johnathan,

    Thank you for reaching out on e2e!

    Jonathan Navor said:
    The doubt is that I don't know how often the samples of the chirps are collected.

    This is something you can calculate depending on your chirping configuration. Please calculate the total chirp time for a single from your radar configuration (used for your data capture from studio) and obtain the interval. Following is a document that can help you out.

    Programming Chirp Parameters in TI Devices

    This will be your sampling rate as you rightly said. With this you should be able to obtain a mapping to the doppler frequency. let me know if anything else is required.

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    TI__Genius 9475 points

    Hi Kaushik,

    Thank you for the quick response. We have another question from the customer. 

    In mmWaveStuido Features there is a section called Frame, specifically 'Frame Periodicity'. Seeing the pdf posted in the inquiry I have arrived at the conclusion that the time between consecutive chirps is the total time of sampling Tp (where Tp is the duration of the chirp) plus the interframe time. 
    This magnitude, (Tp+Inter Frame time) corresponds to the value of 'Frame periodity' specified before the data capture? That is, if a select a 'Periodicity Frame' equal 30ms. The time between chirps corresponds to this value?
    Best regards,
    Jonathan
  • 0 in reply to Jonathan Navor
    TI__Mastermind 20605 points

    Hi Johnathan,

    This is how frame periodicity window can be broken down as.

    Frame periodicity (in unit of time) = Active Frame time + Idle Frame time (Nothing happens on the device until next frame trigger)
    Active Frame time = Total chirping time 
    Total Chirping time = number of loops * number of chirps in a sequence * (Active chirp time + Idle chirp time)

    Single chirp timing contains active + idle chirp time

    See below snapshot-->

    This also depends on your modulation scheme and you would have to calculate the same accordingly.

    Regards,

    Kaushik