High frequency scattering by a double impedance wedge

High-frequency diffraction coefficients are presented for up to and including the third-order interaction mechanisms associated with impedance double-wedge structures. The employed formulation is based on the extended spectral ray method (ESRM) accounting for all surface-wave contributions in a rigorous manner. Key identities are provided to enable an efficient asymptotic evaluation of the resulting integrals via a modified Paul-Clemmow steepest-descent method. The double-wedge structures considered are composed of a common face and outer faces which do not intersect. Examples of the structures studied are the thick impedance half-plane and the impedance insert in a full plane. Computations of the diffracted fields are also presented and found to be in good agreement with corresponding data generated with alternate methods. Some backscatter and bistatic patterns are presented for the purpose of examining the variation of the scattered fields as a function of the wedge angle and impedance