Test of various diffraction theories in the near field of phase objects

Several geometrical, scalar and scattering theories for calculation of diffraction near fields behind phase shifting bars of rectangular cross section and infinite length are compared with microwave measurements. The investigated theories based on electromagnetic scattering are the first Born approximation, an improved version of the first Born approximation and the moment method. Based on a ray-optical approach are the geometrical theory of diffraction (GTD), the uniform asymptotic theory (UAT), the uniform theory of diffraction (UTD) and an empirical boundary diffraction wave for phase objects. Also the well known scalar diffraction theories of Kirchhoff and Rayleigh-Sommerfeld I and II are considered.