Chip antenna through a via

RE: Chip antenna through a via

dingari — Tue, 04 Apr 2017 08:27:25 GMT

Thanks for that clarification. If anyone needs additional info, this post is extremely helpful: devzone.nordicsemi.com/.../

RE: Chip antenna through a via

FormerMember — Tue, 04 Apr 2017 07:34:17 GMT

The matching network in the reference layout is for matching the chip to 50 Ohm. So yes, for matching of the antenna, an additional matching network is needed (shunt-series-shunt).

RE: Chip antenna through a via

dingari — Mon, 03 Apr 2017 16:15:57 GMT

There is a shunt capacitor and series inductor that form a harmonic filter in the reference schematic for nRF52832. Could we use those as a part of the matching network or do we need to have additional shunt-series-shunt components?

RE: Chip antenna through a via

FormerMember — Mon, 03 Apr 2017 12:50:00 GMT

It should work fine to have the chip (nRF52) on one side of the PCB and the chip antenna on the other side of the PCB. When doing so, the antenna matching network should be placed on the same side of the PCB as the chip, because the transmission line will not be a 50 Ohm transmission line when passing through the via hole.

RE: Chip antenna through a via

AmbystomaLabs — Fri, 31 Mar 2017 18:02:18 GMT

But place the antenna matching circuitry close to the nRF. You need a stable ground plane for the match components to work and many chip antennae have an uncharacterized feed like the one in the photo above.

RE: Chip antenna through a via

AmbystomaLabs — Fri, 31 Mar 2017 18:00:23 GMT

Ah, that explains it. You just wanted to reference a solution with a via to the antenna. I get it.

Yes it can be done, but needs matching. If you post photos of your actual board, I will be happy to give you more detailed comments.

RE: Chip antenna through a via

dingari — Fri, 31 Mar 2017 17:53:28 GMT

Hi, those images are not of my board, they are from the Raspberry Pi 3. The pictured chip is not an nRF52 device. I'm just posting them as a reference of a 2.4 GHz chip antenna through a via.

RE: Chip antenna through a via

AmbystomaLabs — Fri, 31 Mar 2017 17:49:49 GMT

Is this really nRF52832? Seems too rectangular for the WLCSP version.

You can feed through a via but it will need re-matching as you have guessed. The current series-shunt-series-shunt you have after the...I'm guessing it is a harmonic filter, should be sufficient to solve the matching problem.

One thing that is not ideal is the antenna is next to a mounting hole. If you use a metal screw to secure the board it will distort the radiation pattern of the antenna. It would be better farther away from the mounting hole.

Also, you didn't make the second ground pad for the micro-coax (hirosi) connector. There should be room to clear out the mask for it.

This board will need some post matching no matter what you do. So if your intention is to avoid this completely, it just won't happen.

Assuming the chip part after the nRF is just a harmonic filter, I would lose the harmonic filter and treat the match from nRF to antenna as one solution. Even with just four components you can easily solve the match and give yourself a harmonic filter for free. This will free up some board space and let you move the antenna a little farther away from the edge.