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Original question:

CC2642R-Q1: RADAR Time of Flight (TOF) - Scientific Principle

CC2642R-Q1: RADAR Time of Flight (TOF) - Distance Calculation

Donatz
Prodigy 190 points
Part Number: CC2642R-Q1

Hi TI E2E Team,

 

Good Day...

 

Regarding the TI TOF Distance Calculation, I am checking an example of the distance calculation...

※please see details below:

RTLS Toolbox > Time of Flight > Theory of Operation > Accuracy

Distance Calculation Example

However, even though the calculation is pretty straight forward, I was not able to achieve the same result.

※please see excel snapshot below :

 

I only managed to arrive on a same result when I performed the following :

① round off the tickavg to the nearest tenths

② divide the distance by 2 

※please see excel snapshot below :


Is this just a typographical error? or I just missed something? which is which?

It would really be appreciated if someone could enlighten this matter...

Best Regards,

  • 0
    TI__Guru** 101460 points

    Hi,

    Don't forget that time of flight (TOF) is based on the round-trip of a packet. The packet has to cover twice the distance between the two devices (PING+PONG).

    Regards,

  • 0 in reply to Clément
    Prodigy 190 points

    Hi Clément,

     

    Thank you very much for the response.

     

    I believe, I am very much aware of the round-trip of a packet, and I did not forget it.

    Based on your answer, you are stating that in order to arrive on the distance you need to divide it by 2.

    However, I think otherwise, this is due to the two reasons below: 

     

    1.  The "18.75 meter" multiplier ( per tick ) was derived, already considering the the round-trip (PING-PONG) time of flight. This is clearly stated in the RTLS Toolbox>Time of Flight>Theory of Operation>Resolution.  Please see below snapshot for the exact definition. 

     

    2.  Based on the example calculation of the distance, it is clear that there is NO "divided by 2" written in the formula. Please see below snapshot.  I think the logical reason behind this, is clearly stated in "1" above. Dividing again "by 2" would cumulatively mean, you are using just 1/4 of the "8Mhz" timer.

    On the other side of the coin, I believe that you are the expert of this subject matter.  And if you will confirm that your answer is indeed the correct, please confirm that final equation below is written incorrectly.


     

     

    Hoping for further enlightenment.

     

    Best Regards,

  • 0 in reply to Donatz
    TI__Guru** 101460 points

    Hi,

    Some for the misleading comment (in fact many users are forgetting about round-trip).

    You are completely correct and the round-trip is taken into account inside the "18.75m".

    The last equation is correct but there was a typo when writing the result. Thank you for pointing it out.

    Best regards,

  • 0 in reply to Clément
    Prodigy 190 points

    Hi Clément,

    Thank you very much for the enlightenment.

    Best Regards,