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AWRL1432：Doppler compensation question

Logen SHI
Prodigy 70 points
Part Number: AWRL1432

Tool/software:

Hi there,
Regarding the gesture_recognition example, I have two questions as follows:

1. Before entering AOA HWA, doppler compensation will be performed on the virtual array (the default waveform is TDM excitation and requires compensation).
I output the values ​​that need to be compensated for each virtual array(), but found that the compensation values ​​output in each frame are different. I would like to ask how this part of the mechanism works?

2. Currently, the gesture mode in gesture_recognition defaults to 2TX_2RX antenna. How will the phase change with this arrangement?

3. After reading the gesture_recognition doc, I found that the document specifically states that TX2RX2 has phase inversion. Can you please explain in detail, or is there any other document that I can refer to?

Best Wishes,

Chen

  • 0
    Prodigy 70 points

    Hi Ti teams,
    The sdk version I use is MMWAVE_L_SDK_05_03_00_02.

    Thank you

  • 0 in reply to Logen SHI
    TI__Expert 8802 points

    Hi,

    Logen SHI said:
    1. Before entering AOA HWA, doppler compensation will be performed on the virtual array (the default waveform is TDM excitation and requires compensation).
    I output the values ​​that need to be compensated for each virtual array(), but found that the compensation values ​​output in each frame are different. I would like to ask how this part of the mechanism works?

    Where are you getting the values you are printing out? I'd expect doppler compensation to be the same per frame.

    Please check out this other E2E post for more information: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1294196/awrl1432-where-is-the-code-location-for-doppler-compensation 

    Logen SHI said:
    3. After reading the gesture_recognition doc, I found that the document specifically states that TX2RX2 has phase inversion. Can you please explain in detail, or is there any other document that I can refer to?

    I don't have any more detailed documents on this, but the analog front end is design in such a way that there is this 180 inversion. The E2E post above explains in more detail as well.

    Regards,

    Tim

  • 0 in reply to Tim Henderson
    Prodigy 70 points

    Hi Tim,

    1. From the copyData_after_2DFFT function in aoaprochwa.c, I saw that the program outputs the value of each virtual array for filtered points (default is 25 points).Please see the actual_address variable in the image above.

    I've figured out that the actual_address input is a signal, but I can't find the relevant code for doppler compensation.

    2. I have seen the E2E post you provided.
    But at the end, he said that because his waveform is set to DDM (Doppler division multiplex) MIMO, there will be no doppler compensation. However, the default setting in gesture_recognition is TDM, so doppler compensation will be generated. In the program and document Doppler compensation is also mentioned (as shown below), so do you mean that doppler compensation is not actually performed in gesture_recognition?

  • 0 in reply to Logen SHI
    TI__Expert 8802 points

    Hi,

    You are correct - I did not realize that other thread was not TDM.

    Let me look at this some more, and I will provide some feedback next week.

    Regards,

    Tim

  • 0 in reply to Tim Henderson
    TI__Expert 8802 points

    Hi,

    I was able to take some more time to look into this.

    Doppler compensation is indeed performed in this gesture demo. The coefficients for doppler compensation are calculated in VectorMult_gen() in gesture_recognition.c.

    You'll see below as well we then set those coefficients to be used in the HWA for the vector multiplication. The vectorRam variable is then used in the aoaprochwa.c to perform the compensation inside the HWA.

    I hope this helps,

    Regards,

    Tim