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IWR1843BOOST: Is range output compensated for doppler effects?

Fong Zi Hao
Prodigy 95 points
Part Number: IWR1843BOOST

Tool/software:

Hi. I am using MRR Lab on the IWR1843BOOST. Is the range output is compensated for doppler effects? For example, let's say we have a target 75 m moving at 100 km/h away from the sensor causing a doppler shift of 14.29 kHz. So, using the 4 MHz/us frequency slope given in the MRR Lab, the beat frequency without doppler effect is 2 MHz, with doppler effect is 1.986 MHz. So the resulting range will be around 74.5 m, 50 cm  away from the ideal result. Is this corrected using the radial velocity obtained in the 2D FFT? May I know which part of the code is implementing this? Thanks.

  • 0 in reply to Fong Zi Hao
    Prodigy 95 points

    Hi, any updates?

  • 0 in reply to Fong Zi Hao
    TI__Guru*** 148974 points

    Hi,

    Please search for "MmwDemo_DopplerCompensation" in the code

    thank you
    Cesar

  • 0 in reply to Cesar
    Prodigy 95 points

    Hi Cesar, 

    Thanks for your reply. After further review, I located the MmwDemo_addDopplerCompensation function in the dss_data_path.c file. Based on the code structure and documentation, I understand that this function handles Doppler phase compensation for virtual antennas. This correction seems intended to align the phase across multiple TX antennas (used in MIMO virtual arrays) to enable accurate angle estimation during the angle FFT stage. However, my concern lies in Doppler-induced frequency shifts that affect range estimation. Specifically:

    1. The Doppler compensation function is called after both range and Doppler estimation are completed, just before angle FFT, which indicates it is spatial (phase) compensation rather than frequency-domain correction.

    2. At line 3109 of the code:
    range = (((float)rangeIdx * obj->rangeResolution) - MIN_RANGE_OFFSET_METERS);

    This line directly computes the range from the FFT bin index (rangeIdx) and does not appear to account for any bias introduced by target motion, especially in the case where only up-chirps are used.

  • 0 in reply to Fong Zi Hao
    TI__Guru*** 148974 points

    Hi,

    This is the only doppler compensation performed. 

    Unfortunately the MRR code does not have very detailed documentation.

    I recommend reviewing the SDK 2.1 for a more detailed documentation

    You can download the mmWave SDK from this link. Please check "Download Options" -> "View All Versions"

    https://www.ti.com/tool/MMWAVE-SDK

    After downloading, please check:

    C:\ti\mmwave_sdk_02_01_00_04\docs\mmwave_sdk_module_documentation.html

    Select "xwr16xx_mmw_Demo"

    Thank you

    Cesar