nRF52840DK Layout

RE: nRF52840DK Layout

Kaja — Tue, 06 Jun 2023 10:49:21 GMT

[quote user="Webster"]I think the layer 3 could meet the same condition for RF reference ground. What are your reasons to choose bottom layer, not layer 3?[/quote]

It was just a design choice done.. so you can use the third layer as well.

[quote user="Webster"]Does this design also help to filter the harmonic power? How does it work? (from your 2nd paragraph reply)[/quote][quote user="Kaja Soerbotten"]We don't have an estimate on how this effects the performance, but what is important is the the output power and harmonics are measured on each specific design and that the radio matching components values are adjusted, so that you get desired output power and low harmonics on your design. [/quote]

The radio matching network works as a filter as well as changing the impedance of the ANT pin on the nRF. So changing the values of these components are necessary to compensate for the difference from the reference design to the costume design.

Best regards,
Kaja

RE: nRF52840DK Layout

Webster Yang — Fri, 02 Jun 2023 06:58:01 GMT

I think the layer 3 could meet the same condition for RF reference ground. What are your reasons to choose bottom layer, not layer 3?

Does this design also help to filter the harmonic power? How does it work? (from your 2nd paragraph reply)

RE: nRF52840DK Layout

Kaja — Thu, 01 Jun 2023 09:09:15 GMT

So, you want the reference ground for the RF path to also be fully connected to the center pad ground. This is why we choose the bottom layer, to have one layer with mostly ground being the reference ground, and to make a proper return path for noise.

We don't have an estimate on how this effects the performance, but what is important is the the output power and harmonics are measured on each specific design and that the radio matching components values are adjusted, so that you get desired output power and low harmonics on your design.

Best regards,
Kaja

RE: nRF52840DK Layout

Webster Yang — Mon, 29 May 2023 00:57:37 GMT

Thank you for your kindness reply, but I still have some questions.

1. why don't you choose layer3 for the reference ground ? (the dielectric thickness between layer 3 & 4 is only 3.9 mils)

2. could you provide how to estimate the shrinking back range and distance?

RE: nRF52840DK Layout

Kaja — Fri, 26 May 2023 12:45:50 GMT

Hi,

it's to reduce stray capacitance, and make the reference ground for the transmission line on the 4th layer.

Best regards,

Kaja