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  • TI Thinks Resolved

IWR6843: Sweep time is too short

Prodigy 60 points

Replies: 1

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Part Number: IWR6843

Hello,

How can I configure a chirp so that the ramp end time (=sweep time) is of the order of 1 ms? I get an error message I try to but ADC sample rate less than 2000 ksamples/second. Nether can I grow the number of  ADC samples to more than 256. We need to improve the snr in the test, and the mobility of the object is low, so the measurement inteval can be hundreds of milliseconds, and Doppler is not needed.

Jarmo Kivinen

Head of Radio Electronics development.

  • Hi, Jarmo:

    You can find the limitation of different chirp parameters.  The largest number of ADC samples is 1024.  

    file:///C:/ti/mmwave_sdk_03_05_00_04/packages/ti/control/mmwavelink/docs/doxygen/html/structrl_profile_cfg__t.html

    You can also increase the number of chirps, because you can combine chirps (through Doppler FFT) to improve SNR.   The largest number of chirp (numLoops) is 255. 

    file:///C:/ti/mmwave_sdk_03_05_00_04/packages/ti/control/mmwavelink/docs/doxygen/html/structrl_frame_cfg__t.html

    But the ultimate limitation is the memory.  The radar cube is saved in L3 and it can not be exceeding 768Kbyte for xwr6843 device, which is 48K samples (assume 4 RX channel, and 4 byte for each sample), which is 20ms active chirping time assuming 2Mbps.    As a summary, you can increase the num_loop, and use rangeFFT and Doppler FFT to achieve high processing gain or high system level SNR. 

    Best,

    Zigang

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