Abstract: The main idea of SBR——shooting and bouncing rays——is discussed in this paper. Using SBR, the EOS of a complicated S-shaped open-ended cavity is calculated. The cavity, with two layers of absorber-lining,has a nonuniform cross section. The cavity curvature is fitted with a series of waveguide configurations, the fitting functions being the simple ones. It is found that the calculated results are in agreement with the measured results.

Key words: spline fit, shooting and bouncing rays, divergence factor, curvature fitting, spline function, radar cross section, curvature matrix