Calculation method and supported range
Ghione–Naldi (1983) grounded conformal mapping. k = w/(w+2g), kb = tanh(πw/4h)/tanh(π(w+2g)/4h); elliptic-integral ratios determine the filling factor and impedance.
Supported tool range: t = 0, 1 ≤ Dk ≤ 20, 0.05 ≤ w/h ≤ 5 and 0.02 ≤ g/h ≤ 5. Assumes infinite side grounds, isotropic dielectric and air above. Actual via fences, ground widths, conductor thickness, pads, connectors, higher modes and dispersion require electromagnetic simulation.
Technical sources
Using the result
The side gap is measured from the signal edge to the coplanar ground edge on each side. The bottom reference must be continuous. Via fences and finite side-ground widths affect real structures but are not represented by this first-pass model.
From a calculation to a released design
Keep the input assumptions with the result. Recalculate when the ordered material, dielectric height, copper or operating conditions change. Confirm the final construction with the fabricator and use field simulation or measurement wherever the simplified model omits an important effect.
See the controlled-impedance guide and material selection workflow for the next checks.