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IWR6843ISK-ODS: Measured and Theoretical Angular Separation

Chen-Chih Liu
Intellectual 340 points
Part Number: IWR6843ISK-ODS
Other Parts Discussed in Thread: IWR6843,

Hi experts,

I'm using the IWR6843-ISK ODS EV board but I refering a document (SWRA549.pdf) to check the angle resolution (separation).

The measurement result from IWR6843 EV board is similar to the document SWRA549, the angle apart should larger than at least 40 degree for scenario of 4 virtual antennas.

Q1: Have any theoretical formula to calculate the "minimum angle apart" instead of measurement?

 

I'm trying to do the demo of "overhead_mount_occupancy". Because of the bad angular separation, the targets at zone 3 (left side on the second row) and zone 4 (middle seat on the second row) cannot be separated easily (or targets at zone 4 and zone 5) and it causes miss alert.

Q2: May I know why TI chose the Capon beamforming to estimate angles (what's the benefit)? Does TI have any suggestion to overcome this situation with the same model?

Thanks,

Best Regards,

Jack

  • 0
    TI__Genius 14415 points

    Hello Jack,

    Please see the following resources on antenna fundamentals and the 3D people counting processing chain. The capon beamforming algorithm is included to increase angle of arrival estimation.

    https://www.ti.com/lit/wp/spyy005a/spyy005a.pdf

    3D_people_counting_demo_implementation_guide.pdf

    Regards,

    Jackson

  • 0 in reply to Jackson Thomas
    Intellectual 340 points

    Hi Jackson,

    It seems to me that you have not to reply my question 1.

    Theoretically, if the dedicated range has only two point targets, 10 degree apart can be separated. The figure shows the simulated result (one target at -5 degree and another at -15 degree)

    It confuses me that my measured result with the EV board should larger than 40 degrees. Do you have any opinion (such as multi-target?)?

    Due to I only can find the measurement result of the 1T4R scenario (SWRA549.pdf), does TI have the measurement result of "IWR6843ISK-ODS" (case of the 2T2R).

    Many thanks,

    Best Regards,

    Jack

  • 0 in reply to Chen-Chih Liu
    TI__Genius 14415 points

    Hello,

    With the capon beamforming algorithm, the angular resolution is reduced to ~15 degrees. But also, two people sitting in the seats will occupy different ranges from the sensor, so the sensor may be able to resolve people at closer angles than 15.

    For the occupancy test, can you please indicate a little more about the test setup? How far are the seats from the sensor and how far apart are the occupants? (in distance or angle)

    Regards,

    Jackson

  • 0 in reply to Jackson Thomas
    Intellectual 340 points

    Hi Jackson,

    Because the performance of VOD was very bad if I installed the sensor in the car, I used the CR to test in the chamber to check (the setting environment was similar to SWRA549.pdf (I extracted and show as below). Due to the limitation of the chamber's size, the distance between the radar to center of two CRs was  60 cm and the distance between the two CRs (x) was 50 cm. The CRs that I used were -20.430 dBsm (L = 0.015 m).

    The figures show my measurement results (angle spectrum at the dedicated range, the x-axis is the angle (deg) and the y-axis is the power (dB)):

    Before the verification, I temporarily skipped the mechanism of "static removal" to see the CR.

    If I remove one CR, the spectrum shows below (the peak is obvious but beamwidth is wide):

    If two CRs exist, the spectrum shows below (Although the two targets can be separated, the peaks are not obvious enough):

    Thanks,

    Best Regards,

    Jack

  • +1 in reply to Chen-Chih Liu
    TI__Genius 14415 points

    Please see some more information about beamforming in the following resources.

    https://training.ti.com/sites/default/files/docs/mmwaveSensing-FMCW-offlineviewing_4.pdf

    https://training.ti.com/awr6843aop-vehicle-occupancy-deep-dive-part-1

    But for the above test, the improved resolution from capon beamforming will only apply to targets in motion, not stationary objects like corner reflectors.

    Best Regards,

    Jackson

  • +1 in reply to Jackson Thomas
    Intellectual 340 points

    Hi Jackson,

    Sorry for the late reply.

    We are trying to setup the measurement environment with vibrating CRs.

    And you are right, the static CR for MVDR cannot be improved.

    Two targets apart are 29.5 degree which can be separated.

    Thanks,

    Best regards,

    Jack