IWR6843ISK: PPL Counting Maximum Velocitiy and Velocity Resolution

Nicolas Wolf

Prodigy 120 points

Part Number: IWR6843ISK
Other Parts Discussed in Thread: IWR1642

Hello,

at the PPL Counting lab there are two different cfg files with the following parameters:

Maximum range: 6.3 meters / 14 meters

Range resolution 5.5 cm / 12 cm

Maximum velocity 23.6 Km/h / 23.6 Km/h

I would say the maximum velocity values should be m/s and not km/h.

Could you please check that for me again? And if my calculations are wrong, could you show me how to do the math correctly.

Thanks in advance!

Nicolas

over 5 years ago

0 Justin Curewitz over 5 years ago

TI__Mastermind 28055 points

Hi Nicolas,

For an explanation of the calculations, please see this document. To convert to m/s, just divide the given values by 3.6

Regards,

Justin

0 Nicolas Wolf over 5 years ago in reply to Justin Curewitz

Prodigy 120 points

Thanks for your fast reply.

In the document there is only the basic formula for Vmax. However, I guess it's not that easy when it comes to setting the chirp parameters in the config file.

My problem is that in my calculations I get almost the same value as in the document of PPL counting. My value: 23.44; PPL Counting: 23.6. But for my calculation it's m/s and for PPL Counting it is km/h.

For my calculation I used the formula from:

https://e2e.ti.com/support/sensors/f/1023/t/689147?IWR1443-Sensing-Estimator-SNR-Calculation

I would be very grateful if you could have a look at my calculation down there:

0 Justin Curewitz over 5 years ago in reply to Nicolas Wolf

TI__Mastermind 28055 points

Hi Nicolas,

Using the IWR1642 conference room configuration as an example:

lambda = c/f, for now lets use 77 GHz as f, so lambda = 3e8/77e9 = 0.0039

Tc = (idle time + chirp ramp time) * 2 (2 chirps per frame) = (30e-6 + 62e-6)*2 = 184e-6

Then lambda/(4*tc) = 0.0039/(4 * 184e-6) = 5.293 m/s max velocity

5.293 m/s *3600 seconds / 1000 m = 19.057 km/h

Regards,

Justin

0 Nicolas Wolf over 5 years ago in reply to Justin Curewitz

Prodigy 120 points

Hello Justin,

Thanks a lot for your example.

One more Question about:

Tc = (idle time + chirp ramp time) * 2 (2 chirps per frame) = (30e-6 + 62e-6)*2 = 184e-6

I thought chirps per frame in this cfg are 128. (frameCfg 0 1 128 0 50 1 0) or am I wrong?

Best Regards,

Nicolas

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IWR6843ISK: PPL Counting Maximum Velocitiy and Velocity Resolution