Plane wave diffraction by a step discontinuity in an impedamce plane

In this paper a high-frequency diffraction of a plane wave by 90-degree step discontinuity in an impedance plane boundary is analysed with the help of uniform geometrical theory of diffraction starting from the Molugenets' solution.
The principal term of asymptotic solution to the problem which is uniform with respect to the angle of the plane wave incidence and angle of observation is derived. The excitation of primary and multiply diffracted fields radiated from the upper edge as well as surface waves is considered (the lower edge doesn't radiate any cylindrical or surface waves owing to the 90-degree step). For simplicity the analytical details are given here for the 90-degree step discontinuity. A similar procedure is followed on the other examples with a more complex geometry.