An incremental theory of double edge diffraction

A novel general procedure for defining incremental field contributions for double diffraction at a pair of perfectly conducting (PEC) wedges in an arbitrary configuration is presented. The new formulation provides an accurate first-order asymptotic description of the interaction between two edges, which is valid both for skewed separate wedges and for edges joined by a common PEC face. It also includes a double incremental slope diffraction augmentation, which provides the correct dominant high-frequency incremental contribution at grazing aspect of incidence and observation. This new formulation is obtained by applying to both edges, the wedge-shaped incremental dyadic diffraction coefficients for single edge diffraction. The total doubly diffracted field is obtained from a double spatial integration along each of the two edges on which consecutive diffractions occur. It is found that this distributed field representation precisely recovers the doubly diffracted field predicted by the uniform theory of diffraction (UTD) and that may be applied to complement ray field methods close to and at caustics. It can be applied as well in all those situations in which a stationary phase condition is not yet well established. Numerical examples are presented and compared with those calculated from both Method of Moment solution and second-order UTD ray techniques. Excellent agreement was found in all cases examined.