GPS antenna scematic for nRF9160

[Jeff Seaman]

Hello

We are trying to finalize the layout we need for a nRF9160 module with gps capabilities.

I have downloaded the schematics and layout for the devkit V0.8.5.

what we need to know is since we are only planning on using the passive gps antenna do we need the two swiches and the full network or can we just use the matching network and the passive antenna.

Also what is the purpose of disabling the passive GPS antenna ?

[Kaja]

Hi Jeff,

we are working on a new reference design, but we only have the one we have for now. 

So the purpose of the switches in GPS-FE is to reduce LTE TX coupling GPS RX, hence avoiding LTE TX-harmonics generation by LNA at GPS front-end. Based on experience; only the series switch is needed.
The switch in series is used as an isolating element from the external interference during LTE, but note; not during GPS RX. So the switch gives isolation, because the LTE- and GPS-antenna have isolation less than 30 dB, and this is the reason why we disables the passive GPS antenna.  

So if you want to simply the schematic, the recommendation I can give you today is: 


Best regards,
Kaja

[arrijal1992]

Hi, I currently working on developing my own hardware.

based on your suggestion, So, I can remove U34 and connecting A2 to C73 directly, right?

regards

[Jeff Seaman]

I got one of the V0.8.5 development kits. they did not populate U34 on the board.  My first test with the GPS showed that it worked just fine looked like 5' accuracy.  So I do not believe c73 is needed.

[arrijal1992]

great. Thanks