# Constructing a GCPW

Create the grounded coplanar waveguide (GCPW) in CADFEKO.

1. Design the GCPW with a specific characteristic impedance using one of the following methods:
• Use a third-party tool (transmission line calculator) to calculate the dimensions of the GCPW.
• Calculate the dimensions of the GCPW using equations from literature.
2. Create the GCPW in CADFEKO using the dimensions obtained in Step 1.
Tip: Use a planar multilayer substrate for the dielectric layer and ground plane.
3. Add vias to connect the ground conductors to the ground plane.
Tip:
• The via spacing should be between $\frac{\lambda }{8}$ and $\frac{\lambda }{10}$ to keep the ground at the same potential and for maintaining a stable impedance.
• The distance of the vias to the center or ground edges affects the impedance. Too close and the vias interfere with the field distribution between the top and bottom plates. Too far and the parallel plate stray inductance increases.