Asymptotic solution for bragg mode conversion in corrugated rectangular waveguide

Rectangular waveguides with nonperiodical corrugation of wall are considered. The Krylov-Bogoliubov-Mitropolsky asymptotic method is used for solving boundary-value problem describing electromagnetic wave propagation in the close waveguiding structure. Mutual transformations of a wave modes propagating in such waveguides are investigated. Analytical solutions for some coupling coefficients are obtained.