Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

chirag.aumraj — Sat, 13 Jul 2019 05:05:35 GMT

Hi Kaja,

Is it necessary to use RF switch between LNA and Antenna? I want to use an onchip GPS antenna on my custom board.

if yes, then why we need to use it?

Thank you,

Chirag

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

Yusuke — Sat, 15 Jun 2019 04:03:43 GMT

Hi, Kaja

I have one more question. How about using saw filter like below? I think you don't need RF switch in this case.

nRF9160(GPS port) --- LNA --- SAW filter --- antenna

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

Yusuke — Fri, 14 Jun 2019 04:43:09 GMT

Thank you!

This is the final design. If you see wrong thing, let me know.

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

Kaja — Fri, 07 Jun 2019 06:42:49 GMT

Hi Yusuke,

so the circuitry in general looks fine, L3 should be the value stated in the LNA datasheet, 8.2 nH. The pi-network out of the GPS pin is not need seen from the chips side, the output impedance of the GPS pin is 50 Ohm.

Best regards,
Kaja

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

Yusuke — Thu, 06 Jun 2019 04:00:44 GMT

Hi, Kaja

This is GNSS circuit of my design.
To reduce power consumption, I want to enable LNA(IC8) only when GPS function is needed. GPS_RF_AMP_EN line controls the enable of IC8.

Also, RF switch(SKY13522-644LF) V1 port is connected to MAGPIO0 port of nRF9160 through RFSW_V1. MAGPIO0 can be controlled by AT command.
Due to the maxium input voltage of SW2, RFSW_V1 voltage is devided and input to the V1 port

I chose ACAG0301-1575-T for GNSS antenna.
https://abracon.com/datasheets/ACAG0301-1575-T.pdf

Can you review this? Thanks a lot!

RE: Is the circuit around GNSS of nRF9160 DK 0.8.5 reliable?

Kaja — Wed, 05 Jun 2019 19:20:51 GMT

Hi Yusuke,

so the DK 0.8.5 has an working GNSS circuitry, and you can design after that.

Your design chooses sounds fine, I'm happy to review the rest of the schematic when its ready.

Best regards,
Kaja