Chip antenna on 4-layer board

[richas]

Hi All,
I am designing a PCB where there will be a wifi module and associated chip antenna on the bottom of the board. There will be a very short trace between the module and the antenna. I need to calculate the trace width such that the impedance is 50 ohms.

The layers go as signal, ground, vcc, and signal. so there will be two substrate layers between the trace and the ground plane. FYI there will be no copper under the antenna itself.

So when I calculate the trace width I assume I add the width of these substrate layers together. What about air gaps left by absent copper? Not an issue? Do I get the substrate thicknesses from the PCB manufacturer?

Thanks

Rich

 

[vedagarbhamsandeep]

The air gaps left by absent copper is just around 17 or 35microns (usually) which can be neglected.

Anyways you can have a quick simulation and check if there would be any changes with / without air gap and I do feel the results would be the same.

 

[richas]

The air gaps left by absent copper is just around 17 or 35microns (usually) which can be neglected.

Anyways you can have a quick simulation and check if there would be any changes with / without air gap and I do feel the results would be the same.

Thank you for the reassurance. Since I have not found anyone addressing this I assumed it was a non-issue but I appreciate the help.

Rich