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AWR1243: ADC Sampling Rate Decimation Factor

Khai Trinh
Genius 4140 points
Part Number: AWR1243

Hi,

I am wondering if the decimation factor to bring down the radar RX sampling rate is configurable? Currently we know that the frequency is 75Mhz. With a decimation factor of 2, that brings it down to 37.5Mhz. Can the decimation factor be set to 3 to bring the sampling rate down to 25Mhz?

Thanks,

--Khai

  • 0
    TI__Guru 69960 points
    Hi,
    There is no option available for application to control decimation factor but using rlSetProfileConfig API it can change the ADC sampling rate in range of 2-37.5Msps.

    Regards,
    Jitendra
  • 0 in reply to Jitendra Gupta
    Genius 4140 points

    Hi Jitendra,

    I have a follow up question about ADC. What is the effect of using RL_ADC_FORMAT_REAL as the ADC data format as specified below besides the data is I only and no Q?

    .adcOutCfgArgs = {
    .fmt = {
    .b2AdcBits = CHAINS_AR1243_DATA_FORMAT_CONFIG,
    .b6Reserved1 = (rlUInt32_t) 0x0,
    .b8FullScaleReducFctr = (rlUInt32_t) 0x0,
    .b2AdcOutFmt = RL_ADC_FORMAT_REAL,
    .b14Reserved2 = (rlUInt32_t) 0x0
    },
    .reserved = (rlUInt16_t) 0x0
    },

    Thank you,

    --Khai

  • 0 in reply to Khai Trinh
    Genius 4140 points
    Would that affect Angle of Arrival calculation for example?
  • 0 in reply to Khai Trinh
    TI__Guru 69960 points
    Making it real ony will effect near field correlation and interference detection (CQ data) and sampling rate requirement as well, as in real type size of sample is half compare to complex type.

    Regards,
    Jitendra
  • 0 in reply to Jitendra Gupta
    Genius 4140 points

    Hi Jitendra,

    Thanks for the answered. In the code under C:\TI\PROCESSOR_SDK_VISION_03_04_00_00\vision_sdk\apps\src\rtos\radar\src\common\chains_common_sample_ar12xx_config.c, number of ADC samples is  configured to be.numAdcSamples     = (rlUInt16_t) AR1243_PROFILE1_RADAR_WIDTH * (rlUInt16_t)2;

    Does 2 here mean 2 bytes per sample whether that sample be REAL or COMPLEX or 2 means it's a COMPLEX sample? In my case in which I would like a REAL ADC sample, what should the configuration be? This is related to your answered about REAL being half compared to COMPLEX type.

    Thanks,

    --Khai

  • 0 in reply to Khai Trinh
    Genius 4140 points

    Also, BeamForm Alg calculate for target energy in the below structure

    typedef struct
    {
    UInt16 velocity;
    /**< velocity or a particular detection. */
    UInt16 range;
    /**< Range dimension for a particular detection */
    UInt16 energy;
    /**< Energy calculated for a particular detection */
    UInt16 angleBin;
    /**< Bin number from the steering matrix corresponding to a particular
    * detection. User is expected to do the mapping of bin to angle
    */
    } AlgorithmFxn_RadarBeamFormObjIdx;

    How was energy calculated and what is its unit?

    Thanks,

    --Khai

  • 0 in reply to Khai Trinh
    TI__Mastermind 30245 points
    Khai,

    The 2 here means it is a complex sample. In the case you want to set real you can remove the multiplication to 2.

    Regards,
    Piyali
  • 0 in reply to Khai Trinh
    TI__Mastermind 30245 points
    Khai,

    The energy is magnitude of the FFT complex number corresponding to the detected point summed up accross antennas in log2 format when it is an input to the beam forming. When output by beam forming it is the magnitude of the complex number corresponding to the peak after beam forming steering vector multiplication. The output is scaled by energyScaling input.

    Thanks and Regards,
    Piyali