Practical geometrical behavior of Knife-Edge Diffraction

This paper presents the scalar knife-edge diffraction (KED) solution is a workhorse for RF and optics engineers who regularly deal with practical diffraction phenomena. Yet the approximate, polarization-independent KED result is formulated in a way that does not provide direct physical insight. In this paper, we demonstrate how the KED formula contains similar underlying physics to other geometrically-based half-screen diffraction solutions. The analysis proves that the diffracted wave emanating from a knife edge is an ideal middle ground between the Sommerfeld solutions for perpendicular (soft) and parallel (hard) polarizations. This justifies the widespread use of KED for radio wave propagation whenever polarization or composition of the diffracting screen is unknown. The GTD coefficient derived in this paper also allows engineers to tackle difficult multiple diffraction problems with geometrical techniques, rather than more cumbersome procedures such as Millingtonpsilas technique.