#17 CPW impedance incosistency

[srj mas]

Using the web interface, calculating the impedance without ground plane, changing thickness from 20 to 18um changes impedance from 55.8982 to 21.8251R. Parameters as follows:

Metal width (W) 500um
Metal spacing (S) 50um
Trace length (L) 2.28752mm
Metal thickness (Tmet) 20um
Metal resistivity (RHO) 1.72e-08Ohm-m
Metal surface roughness (RGH) 0.001mil -rms
Substrate thickness (H) 1520um
Substrate relative dielectric constant (Er)3.38
Substrate loss tangent (tand) 0.002
Frequency 10 GHz

Thank you for the great tool!

[srj mas]

The formulas in the reference for finite thickness impedance are not explained, some of the references there are not accessible. Would be interesting to compare to
"Simplified computation of coplanar waveguide with finite conductor thickness"