NRF54L family BT antenta PCB layout

RE: NRF54L family BT antenta PCB layout

Ressa — Wed, 29 Jul 2026 08:27:34 GMT

Having it more than 0.1mm does not necessary mean it will fail. The recommendation is to reduce the chance of getting emission issue. It is about harmonics radiation and is not related to BLE performance or functionality. All these are for situation that you are going to apply for radio certificates. You can try with 0.2mm if you cannot change it.

Br,

RE: NRF54L family BT antenta PCB layout

ZGa — Wed, 29 Jul 2026 06:52:48 GMT

Hello.

Here is my stackup:

Prepreg distance is 0.2mm, so 0.1 more than you recommended. What does that mean in terms of radiated emmisions? The stackup cannot be changed.

Thank you.

RE: NRF54L family BT antenta PCB layout

Ressa — Tue, 28 Jul 2026 11:43:35 GMT

Hi,

[quote user=""]1.Reference design tells us to ground the single capacitor only to the bottom layer. My design has very poor GND coverage on the bottom layer, so i am wondering, if this rule still applies to my design. It is a 4 layer board with 2nd layer being GND plane. [/quote]

Connecting it to second ground layer is also ok if the bottom layer is not monolithic. It is for harmonics level reduction and the intention is to create a notch filter around harmonics frequencies.

[quote user=""]2. Reference design for the ceramic chip antenna has the last part of the trace inside the polygon cutout significantly widened, so I followed it. However, I'm wondering why the trace becomes so wide. Is it because achieving a 50 Ω impedance inside the polygon cutout requires a much wider trace?[/quote]

If it is coming form antenna reference layout, then the width is not necessarily about impedance of the line. It has to be considered together with chip antenna. So it is part of entire antenna design and most likely is used for fine tuning antenna optimal resonance frequency by changing the electrical length.

Just remember to have your Prepreg value max at 100 um. It is to help further with suppressing radiated harmonics.

Br,
Ressa