Hardware design of the LTE/GPS RF part on custom nRF9160 based board

RE: Hardware design of the LTE/GPS RF part on custom nRF9160 based board

ketiljo — Thu, 29 Oct 2020 14:16:53 GMT

With less bandwidth to cover, you can probably remove the switched all together.

No problem doing a review of your design, just open a private case and upload your design there. Refer to this case.

RE: Hardware design of the LTE/GPS RF part on custom nRF9160 based board

bojan — Wed, 28 Oct 2020 15:28:00 GMT

If we decide to cover a single band or two, we could get rid of RF-switches and cover the band(s) with the single matching network. Correct?

Is it possible for you (Nordic) to review our final schematic and layout designs and give us your feedback?

Thanks in advance!

RE: Hardware design of the LTE/GPS RF part on custom nRF9160 based board

ketiljo — Wed, 28 Oct 2020 15:24:30 GMT

Yes, that will be recommended. Thingy91 is designed for world wide use and covers most of the LTE bands. If you can get away with a single band or two, you can greatly simplify the design.

RE: Hardware design of the LTE/GPS RF part on custom nRF9160 based board

bojan — Wed, 28 Oct 2020 15:21:41 GMT

Thanks for your explanations, ketiljo.

We plan to have the board that will be even smaller compared to Thingy:91. Does that imply it is preferable we take the approach with RF switches in our case?

Cheers,

Bojan.

RE: Hardware design of the LTE/GPS RF part on custom nRF9160 based board

ketiljo — Wed, 28 Oct 2020 14:02:13 GMT

The main reason for using the two RF-switches on the Thingy91 is that the ground plane on the PCB is on the small side. This makes the antenna more narrow banded so the switches are used to tweak the antenna when the band is changed. On the DK, the ground plane is much larger so the antenna is able to cover the whole frequency range.

1. The full frequency range of the nRF9160 is covered by the antenna.

2. Yes, you can cover all bands with a small design.

3. The MAGPIOs will change depending on the frequency the modem is set to. If it's connecting on one band, the MAGPIO will set the correct tuning to cover that frequency. For instance, for band 8, at ~900 MHz, the MAGPIO will be set to 100. https://infocenter.nordicsemi.com/topic/ug_thingy91/UG/thingy91/hw_description/hw_antenna_tuning.html. For B20, it will use 101.