Abstract: The Iterative Physical Optics (IPO) iterative equation is deduced by combining the asymptotic principle of physical optics with the approximations of the surface impedance and reflective coefficient of the PEC surface coated with a thin absorber layer for a large incident angle. The Radar Cross Section (RCS) of an S-shaped circular wave guide and that coated with absorber layer on the inner wall are computed by the fast Iterative Physical Optics method using algorithms of initial value succession and Forward-Backward Iterative. The results show that the absorbent lining and S-shaping of the cavities can lead to 20-dB reduction of RCS for large open-ended cavities.

Key words: large open-ended cavities, iterative physical optics, radar cross section