Calculation method and supported range
Cohn conformal solution: Z₀ = η₀ K(sech(πw/2b)) / [4√εr K(tanh(πw/2b))]. Complete elliptic integrals use the arithmetic-geometric mean. Width synthesis uses bisection.
Supported: t = 0, 1 ≤ Dk ≤ 20, 0.02 ≤ w/b ≤ 5. Both dielectric halves must have the same Dk and thickness. Finite copper thickness, asymmetry, multiple dielectrics, finite sidewalls, higher modes and conductor loss are outside this model. A fabricated board needs a field solver with actual copper dimensions.
Technical sources
Using the result
This model uses an ideal zero-thickness strip centered between planes in one homogeneous dielectric. The full plane-to-plane distance is the spacing input. A mixed-material or asymmetric stripline needs a multilayer field solver; averaging the dielectric constants does not reproduce that structure.
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.