A New Insight into the Role of Hidden Rays in Wedge Diffraction

Abstract

The hidden rays of diffraction provided more accurate diffraction coefficients of some penetrable wedges than the physical optics (PO) solution. However it was not easy to physically explain the existence of the hidden rays on the shadow boundary of wedges. In this paper, a new insight into the role of hidden rays is derived by reinvestigating the diffraction by a perfectly conducting wedge. The exact ascending series solution is expressed in one unique form even if the incidence angle varies. In contrast, both geometrical optics field and PO diffraction coefficients are expressed into three different forms according to the incidence angle. To unify three different expressions of the PO diffraction coefficients, additional PO diffraction coefficients generated by the hidden rays on the shadow boundary should be required. To hide the hidden rays outside the physical region, the angular period of the PO diffraction coefficients should be extended to the edge condition at the wedge tip.