Qi charging and nRF52832 antenna

[Gregor14]

I have developed custom PCB with nRF52832. My antenna layout is very similar to layout present on nRF52DK (PCA10040). All works well. Now, in next prototype, I want to add coil for Qi charging (receiver) with dedicated IC. Due to very limited space, coil will be very close to BLE antenna (see picture).

Some parameters: Coil with diameter 19mm is stick at bottom side of PCB. Here on picture shield is square with side 20mm, but I can (and probably I will) extend it to whole board, except of course empty space where is placed antenna for BLE. Shield with thickness 0,1mm and permeability 200 or more. I'm not using NFC.

I can accept problems with BLE communication during charging. My most important question is about reliability. If I use such solution, is there risk to damage nRF chip or other component on board?

regards, Gregor

[AmbystomaLabs]

Just showing empty white space for the BLE antenna doesn't really help. It would be better if you showed the complete final picture.

From the image though, looks like Qi coil is behind edge of ground plane.  As long as it doesn't interfere with the microstrips feeding the antenna, the coil will likely look like ground plane at 2.4GHz due to its very high inductance. So it should not affect the BLE, but can't say with confidence due to the lack of info in your image.

I would probably worry more about the logic lines you have strewn on the board.  Wireless charging is a lot of field strength at very low frequency.  It will easily trigger gpio.

[Gregor14]

Thanks for the answer. I wasn't enough precise. What you see on picture is not my board. It is know for all of us nRF52DK. Below I attach pictures with same board, but I made zoom in to show antenna trace. My PCB in matter of RLC components and shape of antenna is very similar.

About logic lines, I agree with you. There could be problems. I plan to make two solution: (1) as I mention before, I will cover as much I can bottom of board with shield (not everywhere it's possible), (2) when I detect wireless charging, then (if it will be necessary) few GPIO lines, those are exposed to radiation, I will ground (pull down) - soon I will check it on prototype, how it works.