ENGINEERING ANSWER
Grounded coplanar waveguide depends on trace width, side gaps, substrate height, conductor thickness and grounding structure. The side ground is part of the transmission line, not merely decorative copper fill.
What to decide before release
Choose a solver that includes the finite ground geometry and via placement. Keep gaps consistent through bends and pads, then model the launch separately. Small gap changes caused by solder mask or etching can be significant.
Checks to put in your design brief
- Specify width and both gaps
- Keep ground stitching physically continuous
- Review pad transitions with EM simulation
Important distinction
An isolated microstrip width estimate cannot predict grounded-coplanar impedance simply by adding ground pours afterward.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.