Use COEX0 to switch 3V3 supply to external LNA

[CRD]

We only intend to use an external GPS antenna and have removed all onboard LNA and Antennas. The reference designs for the nrf9160dk show that COEX0 can be configured in firmware to turn off the on-board LNA if an external GPS antenna is used. The reference design (nrf9160dk) always powers the external antenna as it is hooked up to 3V3.

We only need to perform intermittent GPS searches, so for power saving, I am wondering if it would likely work to configure "AT%XCOEX0=1,1,1570,1580" and only power the external antenna via COEX0 switching a 3V3 supply to the external GPS.

We could of course do this with a GPIO and program it, but since we aren't using COEX0 for anything currently and the logic seems to be already included we thought it may be usable for this (or even intended for this use case?).

[mathiaso]

Hi, Colin.

Is it a setup with an external active GPS antenna module, as described here, you are thinking of?

Best regards,
Mathias

[CRD]

Yes it is an active external GPS antenna that includes an LNA in the antenna. 3V3 is fed into the signal output (currently all the time).

The GPS is set in firmware to run a periodic duty cycle ie: nrf_modem_gnss_fix_interval_set(60). And also can be blocked by LTE priority if TX/RX is needed.

I figure that using the coex0 connected to a switch that enables/disables the 3V3 to the signal output would allow power savings as the active GPS LNA will only be powered when the firmware is receiving GPS signal. This would be much easier and less error prone than programming a GPIO ourselves to control the power ON/OFF to the external GPS antenna LNA.

[mathiaso]

Understood.

I guess you have your answer there then, where COEX0 switches the GPS module supply on and off.

[CRD]

Yes that is exactly what we want to do. Thank you.

I'm not sure how I missed the link to the example there.

[mathiaso]

Wonderful, Colin. You're welcome!

Closing the case.