nRF52 antenna: chip vs. PCB? tuning provisions?

[Mike Wirth]

Thanks for the info already provided in devzone.nordicsemi.com/.../

I'm starting a new design with size (and volume) minimization a key requirement. Couple questions:

1. I have the nRF52-DK layout. Is there a nRF52 reference design or app-note besides this?
2. Is there an nRF52 ref design for use with a chip antenna? (by a chip vendor? Any users have experience to relate?)
3. Have the nRF51 layout with a meander antenna (mentioned in the thread above). Can someone provide even a quick hand sketch of how to connect from the unipolar nRF52 RF output to this antenna (with tuning passive components and ground plane offsets specified).
4. Assuming a properly designed 50-ohm antenna, what provisions should be made for passive tuning components between it and the nRF52 chip (to be adjusted after testing)? Same number and type of passives as in the nRF52-DK?

TIA,

Mike

[RK]

1. Yes - look in the SDK and documentation link at the top of this page and under nrf52832 you will find downloadable reference layouts for LDO/DCDC and NFC

2. None I've seen. I just designed one and I'm waiting for the boards to come back, then I'll find out how badly it fails and go from there :) I have some hopes that with the integral balun in the nRF52, a fairly short and hopefully designed close to 50 ohm PCB trace between that and the chip antenna and a chip antenna built for 50 ohms, that I'm going to get some signal out of it at least. If it fails dismally I'll mail one to Norway and see if Nordic can help, and give the guys a laugh.

3. someone else is going to have to reply to that

4. Same advice as the nRF51. If you have an antenna you can tune by length (ie not a chip one) then you need just one shunt component to bring it to 50 ohms, if you are using a chip antenna then you need to design for a pi network where you'll end up populating at maximum two components during tuning. Then in the final design you can just incorporate those two components.

I picked the chip antenna because it seemed like one fewer variable and easier than scraping away at a trace trying to get it to the perfect length.

[bjorn-spockeli]

3: Connect it the same way as the quarter-wave monopole antenna on the nRF52 DK( i.e. with one shunt cap and cutting the lenth when tuning). As for the ground plane offsets, I do not know, but I'll look into it.