Surface impedance approach to calculate loss in rough conductor coated with dielectric layer

The analysis presented herein contains closed-form analytical expressions to calculate attenuation in a layered structure “rough metal-dielectric-dielectric”, which is a practically important problem in separating dielectric loss from rough conductor loss in actual PCB stripline geometries, when measuring dielectric constant (Dk) and dissipation factor (Df) using travelling wave S-parameter methods. This approach is based on the surface impedance concept. It is shown that the presence of an epoxy layer on the conductor may affect extracted dielectric parameters, of a PCB substrate, especially the Df data.