nRF52 Antenna Design Questions

RE: nRF52 Antenna Design Questions

billt79 — Wed, 13 Jan 2016 15:36:02 GMT

After a brief read of the white paper on tuning, i can see that it is somewhat impractical just just put a meander trace onto the pi network of the nRF52, my original plan was to do that an just mess around with the capacitance and inductance values, but the chances of me getting this even close look pretty minimal. Given any values that can be extracted from the altium design, such as size of the ground plane, antenna trace length and resistance, do you think it is possible to work out some rough values for the components in the pi network? As i have mentioned before, then antenna does not need to be perfect, just functional. There is no possible way i could afford the rental or equipment described in the white paper. We have been using the 'cut and paste' approach on all of our nRF51 antennas, and we get some good range from them, even with large variations in the application.

RE: nRF52 Antenna Design Questions

Anders Strand — Wed, 13 Jan 2016 14:46:38 GMT

C15 is there for tuning purposes. Have you read the White Paper about antenna tuning? It might help.

PS. Note the small path to ground in the picture below. This becomes a small inductor, making a filter which removes some harmonic frequencies.

RE: nRF52 Antenna Design Questions

billt79 — Wed, 13 Jan 2016 14:07:47 GMT

Thanks Anders, We don't really have the funds for the hardware in order to tune a new antenna design, which is why we prefer to use existing designs, however in this case we will have to do our own. We don't require optimal range, and nor will it require certification, so we will have to rely on trial and error unfortunately. Thanks for the advice, but i do have one further question, what is the purpose of C15 on the nRF52 DK antenna? I know the chances of use getting a decent antenna from trial and error are slim, but i will just have to make do with what i can get.

RE: nRF52 Antenna Design Questions

Anders Strand — Wed, 13 Jan 2016 12:31:45 GMT

The nRF52 has an internal BALUN, which outputs only one unbalanced connecting for the antenna. You need a small matching circuit between the ANT connection on the nRF52 and the antenna. In addition you must add tuning compononents on the antenna side if that is needed when you do your tuning. In short, use the antenna from the dongle ref design, and the rest from the nRf52 DK ref design.

RE: nRF52 Antenna Design Questions

billt79 — Wed, 13 Jan 2016 11:57:50 GMT

Hi Anders,

I just wanted to ask a couple more things. I do not understand how to connect the meander antenna to the nRF52, on the dongle reference layout, there are two connections to the antenna, where as there is only one antenna pin on the nRF52. I assume this is because some of the circuitry on that antenna is not applicable to the nRF52. Please could you advise me on what parts of that antenna are needed, and how i should go about connecting it. Thanks in advance for your time.

RE: nRF52 Antenna Design Questions

billt79 — Fri, 08 Jan 2016 15:46:43 GMT

Hi Anders, thanks for the quick reply, i wasn't aware that the nRF51 antenna was compatible with the nRF52, i thought the internal Balun would make the design different. We already use the nRF51 dongle antenna on some of our boards, so this would be ideal, Thanks.

RE: nRF52 Antenna Design Questions

Anders Strand — Fri, 08 Jan 2016 15:44:20 GMT

Hey.

Download the reference layout for our nRF51 Dongle. On that we use a smaller "meander" antenna.

When designing wearable products, try to place the antenna in such a way that the radio waves do not have to travel though body tissue. This will reduce your signal strength.

-Anders