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IWR6843: question on beam forming

Charles Jenkins59
Intellectual 360 points
Part Number: IWR6843

How does the 14xx, 16xx and 68xx families of mmWave transceivers steer the beam for applications that discuss a 120° field of view?  I understand phased arrays and beam forming but these types of arrays usually have electronic phase shifters on the TX or RX channels.  The 1443 and 6843 show TX phase shifters but they are described as "binary" which I believe to be either 0° or 180° and are used for interference mitigation.

Q: Does TI use combinations of RX and TX channels and their layout defined phase relationships to "steer" the beam?  Or are there real phase shifters with some phase adjustments other than 0° or 180°?

Q:  Do the ADCs on the receivers simultaneously sample so that there can be multiple angles determined through the FFT?

Q:  When steering the beam, amplitude of TX/RX decreases with increasing angle away from normal to the array?

Q:  If the array were mechanically steered so that data were collected only normal to the array, could the heat map be populated with data from this scan in the capon phase and then this is processed as if the data were electronically scanned?

  • 0
    TI__Guru 50240 points
    Hi Charles,

    These are very good questions and we'll need some time to take a look at this. We will have an answer for you sometime next week.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    Prodigy 200 points

    No problem Akash.  Our goal is 100 meter object mapping and could include people detection and tracking.  I know we can design an array to get the distance we need with our targets but it would have a narrow field of view hence the desire to mechanically scan such an antenna.  Our experiments so far with the 1642 EVM have been disappointing for range.  I have the 6843 and am hoping for better results.

  • 0 in reply to Charlie Jenkins
    TI__Mastermind 25835 points
    Hello,

    There is a application note on "mmWave Radar Sensors: Object Versus Range". www.ti.com/.../swra593.pdf
    This provides details about object versus range capabilities of TI’s mmWave radar sensors.

    In case of 1243P devices: There is a 0º / 180º BPM (Binary phase shift Modulation) and dedicated 5.6º resolution with a 6bit phase shifter control option is provided.

    In 1443 and 1642 devices only 0º / 180º BPM (Binary phase shift Modulation) is available.
    In the next version of IWR6843 dedicated 5.6º resolution with a 6bit phase shifter control is being plan to be added.

    For the question "Do the ADCs on the receivers simultaneously sample so that there can be multiple angles determined through the FFT?"

    Yes, ADCs on the receivers simultaneously sampled for estimating angle of arrival for each of the receive channel. You could review below tutorial on angle estimation from the below link:
    training.ti.com/.../mmwaveSensing-FMCW-offlineviewing_4.pdf
    training.ti.com/intro-mmwave-sensing-fmcw-radars-module-5-angle-estimation

    For the question "When steering the beam, amplitude of TX/RX decreases with increasing angle away from normal to the array" :
    Yes, This would be in accordance with the combined Radiation pattern of the Tx and Rx arrays. Typically at bore-sight you would have highest power and gradually decreases at gazing angles.

    For the question : "If the array were mechanically steered so that data were collected only normal to the array, could the heat map be populated with data from this scan in the capon phase and then this is processed as if the data were electronically scanned?"
    Yes, this is possible, in fact this was the technique used before, electronically steerable beams are implemented.

    Thanks and regards,
    CHETHAN KUMAR Y.B.