The characteristic impedance (Z_{o}) of coplanar waveguide with ground or microstrip lines with signal side ground plane can be calculated using the
active calculator or the formulas at the bottom of the page.

Where ε_{r}= Relative Dielectric Constant

W = Width of gap

S = Width of track

h = Thickness of dielectric

The original formulas are in *Transmission Line Design Handbook* by Brian C Wadell, Artech House 1991 page 79. The formulas use "a" for the track
width and "b" for the sum of the track width plus the gaps either side.

To avoid microstrip line modes, it is recommended that h >> b and that the component side ground extend away from the track on each side more than "b".

Note: For those who wish to understand how K(k) is found, there is a calculator and equations for Elliptical Integrals of the First Kind

This calculator is provided free by Chemandy Electronics in order to promote the FLEXI-BOX

Return to Calculator Index