RE: The HJ-840 SiP module uses the nRF52840 SoC to design the antenna matching network and address layout issues.

YiMing — Fri, 08 Sep 2023 05:35:16 GMT

Thanks, it makes more sense now.

RE: The HJ-840 SiP module uses the nRF52840 SoC to design the antenna matching network and address layout issues.

Bendik Heiskel — Thu, 07 Sep 2023 11:28:48 GMT

Hi,

The trace is so wide because you are using a coplanar waveguide without a ground plane on the bottom layer. If you add GND on the bottom layer under the RF trace the width can be reduced to 1.6mm:

We recommend using this type of transmission line as there is less radiated losses from the trace, compared to a transmission line without a ground plane underneath.

The transmission line does only need to have an impedance of 50 Ohm between the matching networks, so in your case only the part of the trace between C6 and C7 needs to be this width.

As for the rest of the board its best to have as much of the board covered in a GND fill, the antenna performance is dependent on the size and shape of the ground plane, where a larger ground plane usually performs better.

The antenna you are using is designed to be mounted in the corner of the PCB and needs a ground clearance area around it. The antenna datasheet specifies the size and dimensions of this clearance area:

Best regards,

Bendik