RF Antenna signal is internally grounded for nRF52833 and nRF7001

[KN7702]

Hi,

We have developed a custom board with both nRF52833 as the BLE beacon and nRF7001 as WiFi. We have chose to use patch antenna with UFL connector for both. When we tried to write firmware to enable the BLE, we found that the RF antenna signal for nRF52833 is shorted to ground at DC. 

I have also measured the same thing for nRF7001 RF antenna signal. However, this is not the case for nRF5340 RF signal. 

Do both nRF52833 and nRF7001 have RF signal internally grounded? If so, would it have any impact on patch antenna selection? The custom board we designed uses the same matching filter as the reference design, except we did not use the PCB trace antenna but using a patch antenna with center frequency at 2.4GHz.

[ketiljo]

All these have an on-chip balun with the other side of the transformer connected to ground. Hence the ANT pin is DC grounded. There are no DC voltage on that pin so the antenna selection is not affected. 

[KN7702]

I see. So we should be able to use a patch antenna as long as it is tuned at the specific frequency. In this case, for Bluetooth or WiFi, center around ~2.4GHz, right?

[ketiljo]

Yes, any antenna which covers the 2.4 GHz band will work. Center of the band is 2.44 GHx (24002 MHz to 2483.5 MHz)