Is the Nordic Distance Measurement library compatible with FEMs (PA/LNA) such as the nRF21540 or Skyworks SKY66112-11?

[Mathew]

Testing with the Nordic Distance Measurement library has achieved pleasing results while not using a Front End Module, but preliminary testing with a FEM hinted that maybe it isn't possible to obtain accurate distance measurements while using a PA/LNA.

This is mostly conjecture at this point, as there may have been a separate issue with the FEM that didn't relate to the Nordic Distance Measurement library. Nevertheless, I thought it prudent to get an official answer from Nordic about whether there's anything to keep in mind when using the Nordic Distance Measurement library in conjunction with a FEM.

[Simonr]

Hi

The Nordic Distance Measurement library will not work with FEMs I'm afraid, as it is too timing critical to use FEMs with it. There is no support for nRF21540 or other FEMs with NDT.

Best regards,

Simon

[Matthew]

Hi Simon, 

I have tested out the Distance measurement sample, on the nRF21540-DK and found that it functions well out to 10m. 

Just hoping that you may be able to confirm or deny if there is any artificial restraint on measuring distances further, or if this is a direct result of the FEM module not functioning with distance measuring as mentioned above.

Thanks, 

Matt 

[Simonr]

Hi Matt

There shouldn't be a set max range artificially in the firmware, no, as the library at least has been tested at 18 meters on our end, so this sounds like either a FEM issue or an issue regarding the testing environment.

Best regards,

Simon

[PaKa]

NDT doesn't support nor use the FEM so if you try to run NDT with the nRF21540 then you have will lose about 40dB output power for the TX and RX so absolutely not recommended.

[Matthew]

Thanks!