nRF9151 Combined Antenna for LTE and GPS

[BilalMalik]

In the 'nRF91 Series Antenna and RF Interface Guidelines' document there is a section ' 4.3.1 Combined GNSS and LTE antenna example' which shows a potential way to use a single antenna for both GPS and LTE, could you please provide values for the passive components? And also with these values what frequency would the circuit operate over?

[mathiaso]

Hi, Bilal.

Are you thinking of the antenna- and LNA input-matching components? If so, these values these values will differ with different antennas, LNAs, board compositions, product casings, etc., and hence, it isn't possible to provide any fixed values for these components in the datasheet.

The antenna and LNA manufacturers might have some values provided in their datasheets, which might be good starting points, at least for the LNA, I'd suppose. My suggestion would be to check out the datasheets and/or get in touch with the manufacturers of the antenna and LNA you've chosen in order to find out if they have any reference values for these components and if they can assist you with tuning, if necessary.

The nRF9160 SiP's GPS, AUX, and ANT pins are already matched to 50 Ω.

Best regards,
Mathias

[BilalMalik]

Hi Mathias,

Thank you for your response. I am not sure if you can see the image that I attached? The image is from the 'nRF91 Series Antenna and RF Interface Guidelines'. I understand that the matching components will vary depending on different factors but I assume that these designators have been place there for some specific design at a certain frequency? Also with the R1, C7 and C8 on the enable pin, I assume they are there for noise suppression? If you are able to share the reference design with the values that would be really helpful for me to get an idea for my design .  

[mathiaso]

BilalMalik said:

I understand that the matching components will vary depending on different factors but I assume that these designators have been place there for some specific design at a certain frequency?

If you're thinking of the GPS frequency band, this is the L1 band centred at 1575.42 MHz, as stated here. The GPS frequency band is also mentioned in the antenna tuning section of the Thingy:91 documentation.

BilalMalik said:

Also with the R1, C7 and C8 on the enable pin, I assume they are there for noise suppression? If you are able to share the reference design with the values that would be really helpful for me to get an idea for my design .

This should be shown in your LNA's datasheet. However, if using the same LNA as on the nRF9160 DK, you can have a look at the DK's schematic, which is downloadable as part of the hardware files found here.
 

[BilalMalik]

Thanks Mathias? Are there any tuners you are able to recommend that would cover both LTE bands?

[mathiaso]

I'm afraid I can't able to recommend you any specific tuners. You can of course have a look at what is used on the Thingy:91 or the Thingy:91 X, to see if any of these fulfil your demands. Their schematics and BOMs are found in the downloadable hardware files.