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Original question:

AWR1843BOOST: MMwave studio, what's the relationship of chirp duation and duty cycle?

AWR1843BOOST: Processing timing for VOD + VS demo

William List
Expert 6985 points
Part Number: AWR1843BOOST

In the Occupancy Detection + Vital Signs demo, the chirp and frame parameters are as follows:

 

profileCfg 0 77 250 10 40 0 0 98 1 64 2200 0 0 40
chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 2
frameCfg 0 1 168 0 107 1 0

 

From the following thread we calculate the chirp duration to be the sum of idle time and ramp end time:

http://e2e.ti.com/support/sensors/f/1023/t/848804

Using this formula, the total duration for all chirps would be 168 chirps x (40us + 250us) x 2 = 97.4ms. Therefore the duty cycle is 97.4ms / 107ms = 91.02%. This is similar to what mmWave Studio reports.

 

If we assume the following:

Range-FFT => done during inter-chip time (idle time)

Doppler-FFT / Angle-FFT / CFAR =>  done during inter-frame time (after all the chirps have finished and before the next frame starts)

 

The given chirp configuration leaves very little time for inter-frame processing (roughly ~10ms). As such, is there processing happening in parallel on the DSP between the previous and current frame during the chirp idle time? How is this being handled internally?

 

Thanks

Bill

  • 0
    TI__Mastermind 24955 points

    Bill,

    Both the Occupancy Detection and Vital Signs processing chains require a 1D FFT only. A 2D FFT is not required. And the 1D FFT happens in-line while the device is still actively chirping. So by the time we get to the interframe time, the DSP has already completed the 1D FFT on the entire radar cube.

    The Vital Signs processing chain takes less than 4 ms to complete.

    Once the processing is done, the output vital signs information along with the occupancy detection heatmap are stored in separate buffers that can be sent out simultaneously while the sensor is chirping on the next frame.

    Sending out the processed heatmap and vial signs information can happen at the same time while the device is chirping.

    Regards,

    Kyle