A low-frequency wideband metamaterial absorber based on a cave-disk resonator and resistive film

A low-frequency wideband, polarization-insensitive and wide-angle metamaterial absorber (MA) is designed, simulated and analyzed. This MA consists of a periodic arrangement of cave-disk resonator (CDR), square resistive film (RF), and metal ground plane (GP) (a 0.8-mm-thick FR-4 dielectric spacer is sandwiched in between CDR and RF, and another 1.2-mm-thick FR-4 dielectric spacer is inserted in between RF and GP). The simulated results based on the finite integration technology (FIT) indicate that the absorption of the MA is greater than 90% and almost perfectly impedance-matched to the free space in the whole frequency range of 1 GHz-7 GHz. The simulated absorptions under the conditions of different polarization and incident angles indicate that this composite structure absorber is polarization-insensitive and wide-angle. Furthermore, the distribution of the power loss density indicates that the wideband absorptivity is mainly from the composite electromagnetic loss of the CDR and RF. This design provides an effective and feasible way to construct a low-frequency wideband absorber.