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IWR6843ISK-ODS: Measurement Environment of the Demo for Calibrating Antenna Module

According to "Range Bias and Rx Channel Gain/Phase Measurement and Compensation",

does the experimental environment need to be in an RF anechoic chamber? Or in a clean office space?

  • Hi User

    Environment should be an RF anechoic chamber if possible or performed outdoors, but outdoors will not have the same effect.

    Regards,

    AG

  • Thanks for your answer !


    In addition, I would like to ask some details about the experiment.

    1.The document only mentions that the size of D in measureRangeBiasAndRxChanPhase is equivalent to the distance of a few range bins.
        Is there a maximum and minimum limit on the number of range bins?

    2.What distance and size should be chosen for the corner reflector to make the measurement effect better?

    3.Using infrared rays to align the corner reflector and the boresight location should still have errors and produce inaccurate measurement results.
       Which method is best to use to align the corner reflector to the boresight?

  • Hello,

     Typically calibrations are done at zero angle azimuth & elevation.

    Zero-angle calibration refers to the correction applied on each receiver of the chip so that an object at bore-sight is interpreted as at zero-angle. 

    It corrects (or estimates) the relative delay between the Rx paths. Depending on the placement and orientation of the antennas, the applied correction could be correcting either azimuth or elevation angle.

    The distance should be such that the corner reflector can be placed well in far-field zone. The formula given below can be used to calculate the far-field zone.

    If the reflector is very far then reflected signal strength would be weaker compared to clutter & reflections from other objects and cause erroneous calibration results. 

    Hence, somewhere 1-3 meters would be ideal distance. Care need to be taken during the calibration strongest signal should be from the known corner reflector as compared to any other reflection in the scene.

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • As long as my corner reflector is placed in far-field zone and is the strongest reflective target, it will have a well calibration result.
    The size of the corner reflector does not affect any calibration results. Is this correct?

    How about the first and third questions above?

  • Hello,

       Yes, If the corner reflector is placed in far-field zone and is the strongest reflective target then calibration would work well.

    Size of the corner reflector proportional to Radar cross section (RCS). Larger the size higher the RCS, Very large reflection might saturate the receiver, Hence care need to be taken such that Corner reflectors should not saturate the receivers. 

    For the above question 1 and 3 find below answers: 

    1) Very close to DC range bins would cause incorrect values, due to Tx & Rx coupling elevating the Noise floor, To reduce it's effect HPFs are used, high pass filter will have roll off, for the best results you could avoid HPF corner frequency and it's settling region. Best would be to keep around 1-2MHz IF frequency. 

    At larger distance, due to path loss, reflections would be weaker and there could be possibility of clutter dominating the intended target. This sets max limit on the range bin. 

    3) For the best alignment results, you could use the laser pointer between Antenna and corner reflector. Errors below the range resolution could be ignored. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.