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AWR1843: MAX number of ADC samples and MAX number of chirp in one frame

Ray Vincent Aranzaso
Mastermind 18180 points
Part Number: AWR1843

Hi,

Good Day. Customer wants to know the maximum number of ADC samples and maximum number of chirp in one frame using AWR1843 with DCA1000.

I found an answer in the datasheet but I'm not sure if this is the one he needed, please help to confirm. If not, please help to answer his query. Thank you very much.

Best Regards,

Ray Vincent

  • 0
    TI__Mastermind 24955 points

    Ray,

    The relationship between the number of ADC samples and number of chirps per frame has a somewhat inverse nature. This is in the sense that as the number of ADC samples increases, the number of chirps per frame likely needs to decrease in order for all of the radar cube to fit within the shared L3 memory. The table you have provided in your initial post has more to do with power consumption and does not fully address the underlying question.

    In the case of AWR1843, the shared L3 memory has a size of 1 MB (1024 KB). The shared L3 memory is used to store several different outputs, including the 1D FFT output (also referred to as the radar cube), detection matrix (2D FFT output non-coherently accumulated), CFAR results, and Angle of Arrival (3D FFT) results. All of these structures are dependent on the type of profile/chirp configuration used in your particular case.

    For example, let's take the following case:

    • Complex1x mode (this means 4 bytes per sample; 16 bits for the real part and 16 bits for the imaginary part)
    • Number of ADC samples: 256
    • Number of TX antennas: 3 (in TDM MIMO configuration)
    • Number of RX antennas: 4
    • Number of chirps per frame: 64

    The calculation for determining the size of the radar cube is given as follows:

    Radar_Cube_Size = sizeof(ADC Sample) * numTX * numRX * numADCSamples *numChirps

    Radar_Cube_Size = 4 bytes * 3 * 4 * 256 * 64

    Radar_Cube_Size = 786 KB

    In this case above, the radar cube alone with occupy over 75% of the shared L3 memory. Increase either the number of ADC samples or the number of chirps per frame to the next power of two (512 ADC samples per chirp or 128 chirps per frame) would result in the radar cube overflowing the shared L3 memory.

    All of this information is to say that it is important to accurately determine the profile configuration to use in the target application as you can exceed the shared L3 memory without realizing it.

    Feel free to use the equation above as a reference for designing assisting the customer in their chirp development.

    Regards,
    Kyle