Optimisation of a pyramidal geometric transition radar absorbing material loaded with a resistive frequency selective surface

Designs for an improved pyramidal geometric transition radar absorbing material incorporating frequency selective surfaces loaded with either distributed or lumped resistance are presented. It is shown, through full-field simulation, that for a given absorber, the inclusion of impedance loading can reduce the frequency at which a -40-dB reflectivity level is obtained from 6 to 2 GHz. Oblique incidence and variable tolerancing are also discussed.