Uniform and Incremental Formulations for the Diffraction at the Edge of a Truncated Dielectric Screens

A UTD (uniform theory of diffraction) solution is presented for the electromagnetic field diffracted at the truncation of dielectric screens. The formulation is heuristically derived from a revisited exact solution, obtained for the electromagnetic problem of edges illuminated at skew incidence, with surface impedance boundary conditions. The heuristic modification, and a suitable asymptotic evaluation of the integrals involved in the analytic derivation, lead to separate space-wave diffraction and surface wave (SW) diffraction fields, plus typical geometrical optics (GO) contributions for both space and surface waves. Then, starting from this UTD solution, an incremental theory of diffraction (ITD) process is derived, in order to overcome difficulties which are intrinsic in high-frequency uniform formulations (caustics). The ITD formulation is also arranged in a "fringe shape", which is suitable to augment physical optics (PO) scattering predictions