# Microstrip impedance estimate
# Scope: Narrow microstrip approximation for width/height <= 1, zero conductor thickness.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

width = 0.3 mm
height = 0.4 mm
permittivity = 4.2

effective := (permittivity+1)/2+(permittivity-1)/(2*sqrt(1+12*height/width))
impedance := 60 ohm/sqrt(effective)*log(8*height/width+width/(4*height)) [ohm]

check narrow line applicability: width/height <= 1

scenario alternative: width = 0.24 mm