I'm designing a board which contains an LTE module on it. I am a little confused about designing the trace between module and antenna.
As far as I know I need to match these:
- Impedance of module's antenna output
- Characteristic impedance of the transmission line
- Impedance of antenna
Impedance of module and antenna are noted as 50 ohms in their documents. In that case I need to design a transmission line which has characteristic impedance of 50 ohms.
I am planning to use coplanar waveguide with bottom ground layer as transmission line. (2 layers board, 1.6mm board height) I tried a couple of online calculators and Appcad to calculate values for trace width and spacing to get 50 ohms impedance. I couldn't find any suitable values for my design because of pad widths of other components and restrictions of manufacturing process.
Is there any way to match this characteristic impedance with external components, like pi matching network? Or is it just related to trace width and spacing (also dielectric thickness copper thickness etc)
I tried to make an adaptable design. I added a pi network to match transmission line impedance (?). I added a high pass filter which is recommended by module manufacturer. I also added an extra uFL connector to connect VNA. Is it a good way to do like that?