An Introduction to the GTD Edge Diffraction via Equivalent Currents [Education Corner]

The geometrical theory of diffraction (GTD) is a popular method for the analysis of diffraction from edges of electrically large conducting surfaces. It is also easy to use, as it involves only algebraic expressions and geometrical considerations. However, GTD is awkward to teach because a rigorous derivation of the diffraction coefficients requires mathematical skills that are beyond the reach of most students and many practitioners. This article presents an alternative derivation of the GTD edge diffraction equations. This approach begins with a relatively simple stationary-phase analysis of a radiation integral formed from equivalent currents postulated to flow along the edge. This analysis yields expressions in GTD form but with unspecified diffraction coefficients. Diffraction coefficients in the original GTD (Keller) form or the uniform GTD (UTD) (Kouyoumjian and Pathak) form can then be introduced as an alternative to the equivalent currents in the final expressions. This approach is suitable for a concise introduction to GTD edge diffraction for students with no previous experience in asymptotic high-frequency methods.