A composite electromagnetic absorber for anechoic chambers

A composite electromagnetic absorber for anechoic chambers is proposed with the structure consisting of a pyramidal foam and a lossy frequency selective surface (FSS) structure. Simulation results show that the period of absorber array and the pyramid base impact directly on absorption nulls, and the effects of pattern size, surface impedance and substrate thickness of FSS are more complicated due to interactions between the pyramidal foam and FSS structure. Two examples are discussed and the results show that improved absorption below 3GHz can be achieved by properly selecting parameters.