Radar cross section of an open‐ended circular waveguide: Calculation of second‐order diffraction terms

The radar cross section of an open‐ended, semi‐infinite circular waveguide is calculated by the geometrical theory of diffraction and the equivalent‐current (EC) method. We include both single‐ and double‐diffraction terms. It is found that the double‐diffraction term is stronger than the singlediffraction term for the horizontal polarization at wide‐angle incidence. Its inclusion is necessary in order to check with experimental data and the asymptotic expansion of the exact Wiener‐Hopf solution. The EC method is used for the single diffraction. On the other hand the double‐diffraction term is obtained by using the EC method for axial incidence and geometrical theory of diffraction for wideangle incidence. These two solutions are matched with a proper matching function. This technique is computationally more efficient than the matching technique of integration over the equivalent currents.