Hello,
We have product with nRF52811 as Bluetooth receiver and ESP32 as WiFi IC. The ICs have separate antennas, and nRF52811 has LNA with +12 dBm gain connected to antenna input. ESP32 maximum WiFi power into antenna is +10 dBm.
We used to shut LNA off on WiFi activity to protect the nRF52 input, but a recent update to ESP SDK breaks the WiFi activity GPIO control. We have three possible approaches here:
1) Have LNA always on. In this case, we're not sure if the WiFi + LNA power into nRF52 can exceed 10 dBm absolute maximum.
2) Have LNA always off. In this case, our product performance is severely degraded.
3) Use older ESP SDK and live with the bugs in it until a SDK with GPIO control fix is published.
2) and 3) are definitely not ideal, so we'd like to use 1) if we can be sure to not damage the nRF52.
I'm not a RF engineer, so the first question is: Is it possible that RF energy at +10 dBm in WiFi antenna gets coupled at -2 dBm to Bluetooth antenna? The antennas are a few cm away from each other and I have no intuitive understanding if the worry is reasonable or nor.
If there is a possibility of the RF overload of nRF, how we can check the actual levels? We do not have a spectrum analyzer which could verify the signal levels at antenna, but if absolutely necessary we could hire a lab to do it.
However, if it is enough to run stress testing by just run LNA always on firmware on couple units for few days and check if BLE performance does not degrade over time we'd prefer to do that.
Any feedback on our issue? e.g. is the radio coupling between 2 antennas practically always worse than -12 dBm, which would mean the concern is not necessary, or can we test the received power in some destructive or non-destructive way without special equipment?
