2 layer to 4-layer conversion of PCB Antenna design

[Sherry1]

I made an antenna trace on 2 layer PCB.. for chip antenna. This trace was actually coplanar waveguide with ground. So ground and feed trace were on the same plane (Top layer of PCB) And then the Via Holes also made bottom layer a ground plane.

Now I have to move to 4 layer PCB , the distance between Top layer and Ground plane has reduced from 1.53mm to 0.38mm and all my EM Calculation tools for Impedance calulcation are failing. Is 0.38mm too short height between ground and top layer???
Should I move to microstrip in this scenario??
I was using 'Coplanar waveguide with ground' calculator...

I hope there is a strauight forward migration possible between CPW and Microstrip

 

[FvM]

Of course, the tools have no problem with 0.38 mm substrate height. You just failed to set an appropriate trace width (about 0.5 to 0.6 mm).

 

[Sherry1]

Thanks FvM
but if the width is too narrow like 0.8mm then I have matching network problems. Also thinner track means less current, right?

 

[FvM]

but if the width is too narrow like 0.8mm then I have matching network problems.

Why, particularly?

Also thinner track means less current, right?

Yes, it's your decision to use 0.38 mm substrate height and enforce respective low trace width...
If you think a bit, you'll realize that there other possible geometries that can be implemented on a 4-layer PCB. E.g. partly omitting inner layer copper.

 

[Sherry1]

Yes I did consider that, I thought it might not be feasible because layer 2 will be power plane so high voltages might interfere with layer 3 and top layer antenna radiation. So can there be some decoupling or isolation done ?

I am using 0805 capacitors for matching, Ok i admit its not a good excuse:lol: