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AWR1843: Calculation of speed vector in 3D space

Ryan T
Expert 3161 points
Part Number: AWR1843

Hi Team,

Can you help me understand how the "v" vector--the speed vector--in this dataset is being calculated? Initially, I thought it would be SQRT(x*x+ y*y + z*z), but my hand-calculations are incorrect when using this method.

Here's the dataset I'm using from the 1843: 

object

x

y

z

v

0

-0.84426

1.840031

-0.98498

0.026583

0

-0.84426

1.908692

-0.84426

0.026583

0

-0.77391

1.993677

-0.70355

0.026583

0

-0.77391

1.938286

-0.84426

0.026583

0

-1.52437

1.092146

-0.05863

0.318993

1

-1.6768

1.20136

-0.06449

0.318993

2

-1.52437

1.092146

-0.05863

0.305702

3

-1.6768

1.20136

-0.06449

0.305702

0

-2.02272

1.520697

1.231219

0.438616

1

-1.2664

1.05401

-0.36937

0.279119

2

-1.40711

1.171122

-0.41041

0.279119

3

-1.2664

1.05401

-0.36937

0.265828

4

-1.40711

1.171122

-0.41041

0.265828

5

-1.54782

1.288235

-0.45145

0.265828

6

-1.40711

1.190048

-0.35178

0.252536

7

-1.54782

1.309053

-0.38695

0.252536

0

0.369366

0.600372

1.108097

0.09304

Best regards,

-RT

  • 0
    TI__Guru*** 149044 points

    Hi,

    v is the radial velocity of the detected point and (x,y,z)  is the location of the point.

    There is not really a "v' vector.

    thank you

    Cesar

  • 0
    TI__Genius 13276 points

    Hey Ryan,

    Thank you for reaching out regarding your question. The calculation you are using is for the range of an object. The doppler velocity of the object, as shown here, is calculated based off the phase difference from two or more chirps separated by Tc which corresponds to motion in the object. We can obtain the phase through the intermediate signal created by mixing the Tx and Rx chirps. Using the chirp frequency, chirp separation time, and the phase difference, the velocity can be obtained through the following:

    I would highly recommend reading more about the fundamentals of radar measurement through the Radar Academy or watch the TI video series on mmWave radar sensors. Both are great resources if you want to learn more about the theory behind these calculations.

    Let me know if you have any other questions.

    Regards,

    Kristien