Single antenna LTE/GNSS rf switch


We are looking to use the notecard in a very space constrained design where discrete antennas for the GNSS and LTE solution is very challenging, and would potentially have inferior performance to a single switched antenna. We are wondering if the VACT_GPS_OUT can be used with the NBxx (BG95-xx) notecards as an input to an RF switch to tune the antenna for each purpose. For reference, the BG95 documentation outlines GRFC control pins, but they seem to only tune between LTE bands and do not support switching to GNSS.

Can we get confirmation that VACT_GPS_OUT can or cannot be used to control an RF switch for this purposes?

For further context of the design intent, please refer to the Nordic Thingy:91 reference design that switches a single Ignion antenna.

Hey @jascha thanks for posting, and welcome to the community!

Unfortunately, VACT_GPS_OUT cannot be used for this purpose because it does not correlate to GPS/GNSS being turned on or off, but rather the modem being turned on or off, so it would still be high even when in data mode.

When designing the Notecard, we made the decision to not expose the GRFC control pins in order to ensure that customer hardware designs were plug-compatible across Notecards, regardless of the modem we use on the device itself.

Beyond that, I would recommend exploring a multi-port antenna, such as those from Ignion, as they allow for the GNSS and main antenna u.fl to be connected with the same antenna. Ignion provides fantastic antenna design services and I would be happy to make an introduction to them if you want to PM or email me.

Alternatively, you could explore moving away from a PCB antenna as you may end up having problems with a limited ground plane in your space-constrained device. It might be worth exploring something like the W3906B0100 dual-port adhesive flex from Pulse and attaching it to the enclosure, which would avoid the ground plane issue.

I hope that helps!


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