Numerical Evaluation of Absorber Reflectivity in an Artificial Waveguide

The reflectivity of an absorber-lined wall in a shielded enclosure (considered as a metal-backed doubly-periodic absorber array) is calculated by simulating a one-port S-parameter measurement of a single absorber in an artificial waveguide. Compared to real measurements in waveguides or coaxial lines, a much larger frequency range is obtained. By properly taking into account the effect of higher-order modes, a distinction is made between specular and non-specular reflections. The method is applied to two types of hollow pyramidal absorbers to illustrate its usefulness.