QUESTION

Question

Hi,

We are designing a new board that will integrate a GNSS unit and a 3G/LTE module. We are planning the initial placement of the antenna in order to start the layout phase. We have chosen the Raptor and the Inversa antenna models. We are planning a 125mm x 125mm PCB as you can see in the picture we plan to place the antennas in the corners (off course the raptor will have full clearence on the entire length of the PCB.

We have some doubts on the placement of the antennas. The datasheet states that theese antennas should be placed on the shortest edge of the PCB but, as we have a squared design this is not possible. This kind of layout is still valid or we will compromise the performance of the antennas.

Thanks

Giuseppe

Answer 1

Hi Giuseppe,

The majority of boards tend to be rectangular in shape, in which case, the antennas work best on the shortest edge.

In your case, because the PCB is square, any of the corners will be sufficient. Now you should look to position the antenna in the corner that is closest to the wireless module so as to reduce the length of the feed trace.

You have a good size PCB for the LTE antenna and the low bands. So the performance should be very good. Equally the size will give good isolation between the two antennas.

Once your design is complete, we would be more than happy to review your gerber files.

Regards

Colin

Answer 2

Hi Giuseppe,

Yes, the positions for the antennas will be sufficient.  The Raptor should have at least 15mm of clear copper on the left side of the antenna. The Inversa should have copper right next to the left side of it nearest the feed. Be sure to keep the copper keep-outs recommended in the data sheets and the feed traces as short as possible.

Best regards,

Geoff S.