Doubly diffracted ray from a hard quarterplane

The scattering of the electromagnetic field from a half wave dipole source around a quarterplane can be calculated from the solutions to two scalar pr oblems, one with a soft quarterplane and one with a hard quarterplane. In b oth cases, a doubly diffracted ray may exist, but only in the case of the h ard quarterplane does this present a problem. The paper develops the necess ary transition functions for the diffraction coefficients from the exact wa ve solution.