How to calculate the signal-to-noise ratio(SNR) of dw1000?

optimisticgo · July 24, 2019, 3:04am

Hi,
I want to get the SNR of dw1000 ,but I didn’t find a calculation formula for SNR in the user manual.

DecaLeo · July 24, 2019, 2:32pm

Hi
See the section 4.6 & 4.7 in the user manual.
Are you using TREK or EVK? I’m asking as the info attached will be of a help

leo Decaranging CIR_EVK.pdf (372.3 KB)

optimisticgo · July 25, 2019, 1:24am

Thank u for the information. But I still don`t understand the meaning of TotSNR. Meanwhile the calculation method of SNR described in the pdf is SNR=RSL-delta. What is the ‘delta’ ? How can I get this parameter? Attached the screenshot of the SNR information in the pdf.

AndresPrietoGonzalez · March 5, 2021, 9:20am

This might be too late but I’ll write it here just in case someone needs it. This ‘delta’ parameter refers to a variable within DecaRanging software:

Delta value is 87-7.5 and if it’s channel 4 or 7, a -2.5 is added. Now, it would be great that Decawave explained these fixed values as I’m sure these were obtained in some way in their labs. @DecaLeo

DecaLeo · March 5, 2021, 9:03pm

Hi,
Using the convertion from dBm to mW and multiplication and covertion back to dBm you will get the following.

First you need to convert dBm to mW:
-41.3dbm = 10^(-41.3/10) = 0.00007431 mW

Secondly you need to convert from 1 MHz to 500 MHz (Ch2/Ch5) or 900Mhz (Ch4 /Ch7)

0.00007431 mW * 500 = 0.037065512 mW
0.00007431 mW * 900 = 0.066717922 mW

Finally you need to convert to dBm again:
10 * log10(0.0370655) = -14.310299957 dBm/500MHz

10 * log10(0.066717922) = -11.757574906dBm/900MHz

And see, around 2.5dBm is the difference.

I used dBm to mW conversion calculator for a bit of help

AndresPrietoGonzalez · March 8, 2021, 9:07am

Hi @DecaLeo, thanks for the quick answer! That makes sense!

Could you also explain the 87 and the 7.5 values (which you end up calculating 87-7.5)? We are working with this and it would be really useful for us to understand these parameters.

Thanks!

DecaLeo · March 8, 2021, 6:46pm

Hi again,
Again a calculation…
The 87 refers to thermal noise: The thermal noise at room temperature in the 500MHz is ~-87dBm.

This is computed from kTB

k is Boltzmann’s constant (1.3806504x10^-23)
T is temperature in Kelvin (~300K)
B is the bandwidth
Just fill in T ( degrees or Kelvin) and B (500Mhz).
Thermal Noise Power Calculator - Everything RF

The 7.5dB is the nominal antenna referred noise figure in the reference board. This figure will change from design to design.

For further info on this search for kTB noise on the web.

Stay Safe
Leo