Higher-order impedance boundary condition in coordinate-free form

This paper presents a new coordinate-free dyadic formulation of the higher order impedance boundary condition for rotationally symmetric homogeneous bianisotropic and longitudinally inhomogeneous isotropic layers, in which the differential operators acting on fields are expressed as the second order polynomials in the normal derivatives. The obtained results provide an excellent simulation of electromagnetic properties for the stratified structures and can conveniently be used to simplify the complicated manipulation for the solution of the given boundary value problems, especially in problems of a guided wave propagating along the direction normal to the structures.