nrf52840 configuration and Antenna design for custom board

[Moghees]

I want to design custom board for nrf52840. I will be using configuration 5 from Reference Circuit nrf52840. I do not want to use NFC can I leave NFC pins not connected. For antenna design can I use the antenna design in nrf52840 DK?

[ketiljo]

Yes, the NCF pins can be left floating as any other GPIO not in use. 

For the RF section, you can use the DK antenna and matching network. Note how C3 is grounded.

[Moghees]

Thanks and If I remove the RF connector shown in blue box will there be any problem?
or
Should I place 0R resistor in place of it?

[Moghees]

I have another question if I want to expose the SWD interface of nrf52840 and I am powering the custom board with battery what care should I take?
If you can refer me to some document that I can see for reference?

[ketiljo]

You can just remove the connector. No need for a resistor here. For measurements on the radio or the antenna, just cut the track and solder the coax to the ground plane / track.

[Moghees]

Thanks

[ketiljo]

Other than general ESD protection. SWDIO has internal pullup, SWDCLK has internal pulldown. In case these aren't sufficient, it's a good ideal to at least have space for external resistors to make the design more tolerant against noise.