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Compiler/AWR1642: Doppler Compensation // What is this from the sensing point of view?

George Denove
Expert 1435 points
Part Number: AWR1642

Tool/software: TI C/C++ Compiler

Hi,

I am trying to recreate the onboard DSP chain in MATLAB for the AWR1642 since I have a network of AWR1642's receiving both monostatic (what TI DSP Chain is used for) as well as bistatic data (what my recreated DSP chain will accomplish), I am trying to fuse together a network worth of AWR1642 data rather than data just from a single node.

Therefore, I was looking at TI's doxygen documentation for guidance and while I was looking specifically at the BPM configuration section/implementation of the DSP chain, I noticed there was a specific Doppler Compensation used. So my first question is: what is this doppler compensation used for in the 2D FFT from a sensing point of view?


Then, I went into the TI source code to try and figure it out, specifically, dss_data_path.pp starting on line 2276, I noticed two variables that went into the doppler compensation: expdoppcomp and azimuthval. They both affect the Real and Imaginary part of the 2D FFT. Question (2), how do expdoppcomp and azimuthval affect those real and imaginary components of the doppler compensation? Does the magnitude change?

I also noticed some unknown functions like, _ssub and _loll?

Finally, (3) Once you have found the doppler compensation, do you just add doppler compensation to the phase of the received antenna to determine how much to rotate the old signals phasor?

Thank you so much for the help. If I can get clarification on this, this would help solve a large part of the misunderstanding I am having with this part of the code.

All my best,

George

  • 0
    TI__Guru*** 148804 points

    Hi,

    There is some documentation in an older version of the sdk that may be more clear. Not sure if you have seen it.

    To download an older version of the sdk please check link for previous release at bottom of release page

    file:///C:/ti/mmwave_sdk_02_01_00_04/packages/ti/demo/xwr16xx/mmw/docs/doxygen/html/index.html

    Also regarding doppler compensation please also check a radar signal processing textbook

    thank you

    Cesar

  • 0 in reply to Cesar
    Expert 1435 points

    Hi Cesar,

    So, TI's doppler shift compensation (DSC) implementation is no different than a radar signal processing textbook's implementation? And I understand in general what doppler compensation is, but I guess to solidify my knowledge: we use DSC because we average two chirp responses in one block to receive the signal out again? I may just not understand why TI uses DSC in your specific implementation of BPM on one AWR radar.

    And I was able to retrieve the 2.0 SDK version.

    My other main questions though were revolved around the two main variables (expdoppcomp and azimuthval) and how they affect the real and imaginary part of the doppler compensation?

    Thanks

  • 0 in reply to George Denove
    TI__Guru*** 148804 points

    Hi

    Yes, the doppler compensation is similar to what is provided in radar signal processing textbooks

    Unfortunately I don't have more information than what is provided in the documentation.

    Thank you

    Cesar