Microwave scattering from dielectric wedges with planar surfaces: a diffraction coefficient based on a physical optics version of GTD

The development is presented here, derived from a physical optics version of the geometrical theory of diffraction (POGTD) of a simple edge coefficient for external and internal diffraction at planar dielectric edges. This is required in connection with a simulator for synthetic aperture radar (SAR) images. The diffraction coefficient is assessed by comparison of calculations using POGTD, excluding multiple scattering processes, with an extensive set of experimental microwave scattering data on dielectric wedges and some corresponding calculations by the finite-difference time-domain method (FDTD) of solving Maxwell's equations. The experimental results were gained from dielectric wedges of four wedge angles, each for a wide range of angles of incidence, separately for TE and TM plane polarized components, and for two sets of wedges with different dielectric constants. The intensity distribution found by using the diffraction coefficient for external diffraction is found to be in good agreement with both experiment and calculations using FDTD. For internal wedge diffraction, POGTD predicts an intensity distribution of similar angular shape to the experimental one but, due to the neglect of absorption, the intensity level is too high.