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AWR1243: Tx phases are not the same

Igor Frol
Prodigy 70 points
Part Number: AWR1243

Hi, experts!
Our team working with custom radar board. My question is about internal Tx calibration in AWR1243P chip.

We were trying to detect corner reflector by MIMO array and have found some artefacts in azimuth profile.Our MIMO array configuration is simple: 4 Rx with lambda/2 spacing and 3 Tx with 2*lambda spacing.
We have found that phase of corner reflector signal changes linearly beetween 4 Rx. But phase has the gap between Tx switching.
We were trying to use rlRfInitCalibConfig() but this did not resolve the problem.

Does rlRfInitCalibConfig() enable Tx phase clibration? Which facilities AWR1243P provide to overcome this issue? Do we need to use external calibration matrix?

Thanks!

  • 0
    Prodigy 70 points

    To illustrate the problem I have attached some figures.
    The top one illustrates phase discontinuities over 12 Rx MIMO antennaes (4 Rx and 3 Tx). This discontinuities looks like Tx transmission line delays.
    The bottom one illustrates the corresponding azimuth FFT over MIMO array. Our test scene had a single target. The azimuth profile has computed for corresponding range-Doppler bin.

  • 0 in reply to Igor Frol
    TI__Expert 7215 points

    Hi Igor,

    I am not sure if I understand your question. Given TXs are separated by 2*lambda the phase measurement from different TXs would have discontinuity. You need to use this Phase information across multiple TX and RXs to form your MIMO array.

    If you need more details on MIMO processing, please refer to MIMO scripts in mmWaveStudio or in Radar SDK code

    Regards,

    Kaushal

  • 0 in reply to Kaushal Kukkar
    Prodigy 70 points

    Hi Kaushal, thanks for reply.

    We made a mistake in the order of the antennas in MIMO array. We reordered signals and this has eliminated side peaks in the azimuth profile. 

    But we can still observe some phase irregularities between the four antennas (Tx switching). Our antenna array design has high accuracy and Tx transmission line delays are the same so we can assume that it is the internal (transmitter) difference in initial phase of signals. We expected that internal Tx calibration with rlRfInitCalibConfig() to eliminate the irregularities but issue kept.

    So question is: how we can remove phase gaps between Tx? The exetrnal calibration matrix only?

  • 0 in reply to Igor Frol
    TI__Expert 7215 points

    Hi Igor,

    Inter chip TX channel and phase mismatch needs to be done externally. Please refer to Section 8.3 of mmWaveStudio 3.0.0.14 user guide for more detailed steps

    Also refer to AWRx_TX_Channel_Calibration_Script_User_Guide in mmWaveStudio\MatlabExamples folder for detailed explanation

    Regards,

    Kaushal