Asymptotic solution for Bragg reflection of surface and volume waves on nonperiodically inhomogeneous impedance rod

The consideration of electromagnetic wave propagation in open irregular waveguiding structures usually assumes either smooth varying of medium parameters or their rigorously periodical perturbation. Combination of smooth and oscillated parameter perturbations leads to additional peculiarities of Bragg scattering. Anisotropy of parameters causes coupling of waves with different polarization. In the present paper using complex form of asymptotic method of Krylov, Bogoliubov and Mitropolsky (KBM), mutual transformation of waves in open guided structures in the form of an impedance rod with spatially oscillated surface impedance has been theoretically considered. Influence of exiting of surface waves propagating along the impedance rod on scattering wave beams has been analyzed. For some types of perturbations the solutions of coupled-wave equations of KBM method have been obtained and expressions for perturbed wavenumbers of eigenwaves have been derived. In general case the differential equations with slowly varying coefficients are rather easily integrated by a numerical method. Longitudinal distributions of wave complex amplitudes describe combination of different physical phenomena in examined structure.