NRF52840 Poor Radio performance

RE: NRF52840 Poor Radio performance

Andreas — Tue, 20 Nov 2018 14:50:53 GMT

Hi,

The bottom layer looks fine.

Soldering a wire on will likely not be the correct length and it will not be matched (missing a shunt cap). Regardless, you are welcome do sent me one of your boards to optimize the output power, match the antenna. We offer to do this for all our customers, just let me know if you are interested. If there actually is a problem with the nRF52840 I willalso work that out.

Best regards,

Andreas

RE: NRF52840 Poor Radio performance

Gaétan — Tue, 20 Nov 2018 14:19:55 GMT

Hi Andreas,

My board is composed by only 2 layers:

I need to precise, that I think there is a problem with generated power on nRF52840...

Because, when I try with the first Pi filter like nRF52840DK and a wire, the RSSI is very low (about -85dBm) compared with nRF52840DK (-40dBm) at the same distance.

Regards,

Gaétan

RE: NRF52840 Poor Radio performance

Andreas — Tue, 20 Nov 2018 11:52:33 GMT

Hi,

The board thickness is not too important and not specified to be 0.8mm, if anything it is specified to be 1.6mm but as I said it is not that important.

Without having seen your internal/bottom layer, I am quite certain this has to do with your antenna. L2 =3.3nH and L3=1.5nH are valid for the Johanson test board, in a different board they will be different. See this whitepaper.

Obviously, if you e.g. do not have ground underneath, or if you have ground underneath the antenna, that will also contribute negatively. If you share your other layers also I might be able to say something.

C14 = C13 = 1.0pF and L1 = 3.9 nH are possibly not optimal for your design, but should not have an effect this large.

Best regards,

Andreas