Radio measurements on the Bluetooth antenna
Nordic Semiconductor has performed tuning of the BLE antenna as well as did a quick check on GPS and mobile antenna (note the latter did not have the tuning applied yet). A set of value changes has been suggested as shown below. No geometry changes are required.
Performance improvement with tuning
- Bluetooth: around -73, -75
- Bluetooth: between -60 and -70
This setup is very approximate as RSSI value jumps a lot inside NRF scanning tool. In summary, nRF52811 performance is about as expected: output power is ~1-2dB down due to the coexistence filter. Unsuccessful improvement to raise the output power at all channels, if one channel was improved the other two were made worse. Harmonic emissions have loads of margin to any requirement though, so not recommend making any changes to C90 or L24.