, nearly all the electric field in confined in the dielectric
substrate, just like a parallel-plate capacitor, and we have
For a narrow strip, where
, the electric flux lines are almost equally distributed in
the air and dielectric, hence
For a wide strip, where , nearly all the electric field in confined in the dielectric
substrate, just like a parallel-plate capacitor, and we have
For a narrow strip, where , the electric flux lines are almost equally distributed in
the air and dielectric, hence