Abstract
A spectral-domain-rational-approximation approach is presented for systematic derivation of higher-order impedance boundary conditions for complex stratified coatings, consisting of stacked homogeneous-(bi)anisotropic and (radially) inhomogeneous-isotropic layers, laid on (locally) cylindrical conducting surfaces. Second-order impedance boundary conditions are shown to provide accurate results even when the local curvature radius is a fraction of a wavelength.