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IWR6843ISK: Question about TX channel order difference in chirp configuration (IWR6843ISK, Long Range People Detection)

JAEHOON KIM
Intellectual 445 points
Part Number: IWR6843ISK


Dear TI Support Team,

I am analyzing the Long Range People Detection project using the IWR6843ISK board, and I have a question regarding the chirp configuration and TX channel order.

According to the default configuration provided by TI, the chirp settings are as follows:

chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 4
chirpCfg 2 2 0 0 0 0 0 2

In this configuration, the TX channel order is TX1 (Azimuth), TX3 (Azimuth), and TX2 (Elevation).

However, if I change the chirp configuration as below:

chirpCfg 0 0 0 0 0 0 0 1
chirpCfg 1 1 0 0 0 0 0 2
chirpCfg 2 2 0 0 0 0 0 4

the TX channel order becomes TX1 (Azimuth), TX2 (Elevation), and TX3 (Azimuth).

I would like to know what specific difference this change would cause in terms of signal processing or virtual antenna mapping.

From my understanding, when the TX order is set as TX1, TX2, TX3, the function AoAProcDSP_dopplerCompensation() seems to apply different cosine and sine values to RX1–RX4 for TX2 and TX3, compared to the original configuration.

Could you please clarify how this TX channel reordering affects:

  1. The virtual antenna configuration, phase compensation within AoAProcDSP_dopplerCompensation, and overall AoA (Azimuth/Elevation) estimation?

Thank you for your support.

Best regards,
Jaehoon Kim

  • 0
    TI__Mastermind 24167 points

    Hello,

    You are right where doppler Compensation is where this can get tricky. More information on the AoA proc can be found in

    C:\ti\mmwave_sdk_03_06_02_00-LTS\packages\ti\datapath\dpc\dpu\aoaproc\docs

    Also, is there a reason you are trying to switch the TXs when the demo is designed to use it the default way?

    Best Regards,

    Pedrhom

  • 0 in reply to Pedrhom Nafisi
    Intellectual 445 points

    Hello Pedrhom,

    We’re not aiming to change the TX ordering for deployment. We ran two quick comparisons because the results raised a question.

    Setup: We used the mmWave Industrial Visualizer to load CFG files.

    CFG A: TX chirp order 1–2–4.

    CFG B: TX chirp order 1–4–2.

    Input: A fixed test pattern so the coordinate values stayed constant.

    Observation: The point-cloud outputs looked essentially the same for both CFGs. That made us wonder whether changing the TX order should have any practical impact in this demo.

    Best regards,
    [Jaehoon]

  • +1 in reply to JAEHOON KIM
    TI__Mastermind 24167 points

    Hello Jaehoon,

    I am not sure how extensive your testing was and what kind of configuration you used, but its possible that there wasnt enough of a change to show possible inaccuracies when switching the TX order and nothing else.

    Best Regards,

    Pedrhom