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Oblique incidence optimisation of a pyramidal absorber using a frequency selective surface

This paper presents a topology for improving the low frequency performance of pyramidal radar absorbing materials at oblique angles of incidence. The technique uses an embedded frequency selective surface as an impedance matching layer and improves the −40dB reflectivity limit from 6GHz to 4GHz for 102mm pyramidal absorber. The frequency selective surface is based on a resistively loaded dipole FSS and simulations of optimised results of the modified RAM structure are presented.