GPS Antenna Circuit

[Balamurugan]

Hi,

we are progress of designing custom board using nRF9160.

By reading nRF documentation, my understanding is GPS circuit in Dev kit is unstable/nonperforming.

Could you please share new/updated GPS antenna section schematic.

Also please suggest smd small size ceramic antenna for Cellular-RF.

Thanks.

[Andreas]

Hi,

 

Correct, the GPS circuitry in the current version of the DK is too complex and not performing very well. See the PS reference design for outlines of the general design. In general:

• Green: LNA with LNA specific passives. We recommend an LNA that has the filter on the input.
• Blue: Test connector - optional
• Red: PCB antenna + antenna matching

 

You can also use an external antenna, depending on your product requirements. If using an active antenna, you would need a bias tee on your PCB.

 

You should choose a PCB antenna which has a recommended mounting that aligns well with your intended mounting. E.g. if it is recommended to be placed in the corner of a ground plane, it will not be optimal if you place it along a straight edge of the ground plane. You also need to ensure that it supports the frequency in which the bands you plan to use are placed.

 

Best regards,

Andreas 

[Balamurugan]

Thanks for pointing to new GPS circuit and explanation.

we do not find "QM14501"" in digikey or mouser to buy.

Could you recommend alternative component. 

[GJSea]

The Infineon BGA715N7 is what I'm going be basing our design on, it is readily available and has much higher 20dB gain, and uses less than half the current.

[Andreas]

Hi,

 

Unfortunately we do not have much experience with different parts yet. Skyworks has a nice lineup though, both sole amplifiers and front-end modules (with filter). 

Depending on the design, and the isolation between the antennas, it might also be needed to add a mechanism for disconnecting the GPS antenna during LTE transmission, e.g. the switch circuitry in some of the DK designs. We have not managed to characterize the general need for this yet. In any case, from a performance point of view, it should be in your best interest to place the two antennas as far apart as possible, which should increase the isolation.

 

Best regards,

Andreas

[Andreas]

Hi,

 

This looks fine, but note that as there is no filter internally this might be needed externally.

 

Best regards,

Andreas

[Yusuke]

Hi, Andreas. I'm designing a circuit related to gps antenna in nRF9160.

you said this.

>note that as there is no filter internally this might be needed externally

If you add a RF switch between GPS antenna and LNA(BGA715N7), it should work fine with BGA715N7, right? In my understanding, you need to select LNA equipped with filter only when you don't attach RF switch. Is this correct?

[Hardik]

Hi Yusuke,

We can use Band pass filter or RF Switch.

Are you done with your schematic part of GPS?

[Yusuke]

Yes, I did. Now, I'm doing impedance matching.