NRF52832 PCB Layout Review

RE: NRF52832 PCB Layout Review

JONATHAN LL — Tue, 01 Feb 2022 09:33:31 GMT

Hi,

Just want to clarify somethings regarding the antenna and ref designs.
- there is not antenna in the circuit reference design only a radio matching network.
- we do have antenna reference in our DK hardware files.

So if you where to follow only the circuit reference design then you would not have an antenna, so you need to include an antenna in the design or else you will not be successful wit radio communication.

You can gett the HW files for the DK here:https://www.nordicsemi.com/Products/Development-hardware/nRF52-DK/Download?lang=en#infotabs

"A matching network is needed between the RF pin ANT and the antenna, to match the antenna impedance (normally 50 ohm) to the optimum RF load impedance for the chip." and " All the reference circuits are designed for use with a 50 ohm single end antenna."

So that means that you should make sure that it is matched on both the chip side and the antenna side.

Here is a rough illustration of what a schematic could look like. So here we have the C3 and L1 as the matching and filtering components for the radio pin, and then we have the transmission line that leads to the the antenna matching components. We often do recommend a full pi network but it is not always needed, as you can see in our DK design we use a PCB trace antenna only have a singel shunt capacitor so that would be Z3 in the illustration above.

So to be able to use the PCB that you have shared here with me for any type of radio communication then you need to add a antenna, i did a rough sketch to illustrate what that could look like.

[quote user="Marshal"] How crucial is antenna size and shape?[/quote]

It has major impact on the performance.

[quote user="Marshal"]Lastly is the tuning process changing L's and C's, or would it require a whole new board spin?[/quote]

There will be two tuning processes, one would be for the radio, to ensure that it provides enough power and that it filters the harmonics sufficiently. Then there is the tuning of the antenna, to make sure that it is 50 Ohm and a low enough VSWR. We at Nordic can provide this services.

Regards,
Jonathan

RE: NRF52832 PCB Layout Review

Marshal — Tue, 01 Feb 2022 02:57:35 GMT

Thanks Jonathon. That's helpful. I've updated the layout based on your suggestions:

After looking at the designs I increased the antenna length. The antenna is much different on the DK files. How crucial is antenna size and shape? Lastly is the tuning process changing L's and C's, or would it require a whole new board spin?

Thanks again.

RE: NRF52832 PCB Layout Review

JONATHAN LL — Mon, 24 Jan 2022 10:11:55 GMT

And remove the connection to top layer ground for the first capacitor

It is to improve filtering of harmonics as well as matching.

RE: NRF52832 PCB Layout Review

JONATHAN LL — Mon, 24 Jan 2022 10:09:27 GMT

Hi,

We at Nordic do HW reviews so if you want that then we can provide feedback, only have to share schematic(PDF) and layout files preferably Gerber or PDF.

[quote user=""]Will this require changing the RF tuning elements to get good performance? [/quote]

Yes, potting the device will effect the antenna performance. Exactly how much is difficult to say. There is potting material that does not have as huge of a impact then others for example. Only way to figurer out wat is best is to test and tune accordingly.

You can check out the PDF, id does include alle the layers for HW layout, it might be smart to look at both DK files and SoC files.

You can also see the guidelines at infocenter: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/ref_circuitry.html?cp=4_2_0_52_7#layout

So for a 2 layer PCB we have the keep out only on the top layer. If you have more then two layers, we recommend that you include the cut out on internal layers also.

If you dont want to share entire project publicly you can create a new private ticket.

Regards,
Jonathan

RE: NRF52832 PCB Layout Review

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