Imp006 RF tracing width

Hi Electric Imp,

Looking at your reference design for Imp006 in Altium, I can see that the RF traces, which must be 50 ohm, for GNSS and Cellular has a width of 0.8mm.
However, in the design rules 50 ohm traces is set to 0.325mm, which is also what I get when I calculate the width of a transmission line with the given layer stackup.

Can you enlighten me, why this is the case?

Best,
Mathias :slight_smile:

50 ohm trace width depends on your board stackup, and what option you’re going with for impedance controlled traces.

The “thick” trace is a coplanar waveguide, not a microstrip, so has different rules to get to 50 ohms. Due to the large amount of power that can go through the cellular TX path (+33dBm for 2G) this is advised.

See the Quectel appnote: https://www.quectel.com/UploadImage/Downlad/Quectel_RF_Layout_Application_Note_V2.0.pdf

Of course, that makes sense.

Thanks for your quick reply.