An ultrathin microwave metamaterial absorber with enhanced bandwidth and angular stability

A very thin metamaterial absorber with enhanced bandwidth and angular stability is designed and its application in radar cross section (RCS) reduction of antenna is discussed in this paper. First, a wideband absorber element consisting of an unconnected square loop and unconnected printed cross on a metal backed FR-4 dielectric is designed. This structure has full width half maximum bandwidth of 0.41 GHz and exhibits polarization independent JPCOcharacteristics. It also shows good absorption characteristics for incident angles up to 40° for TE and TM polarized wave. Further enhancement in bandwidth up to 0.574 GHz is achieved by arranging the structures with overlapping resonances as a 2 × 2 array. This 2 × 2 array is used as the unit cell for the larger array. This structure also exhibits polarization independent characteristics and good angular stability up to 60°. The values of effective permittivity and permeability are retrieved from the reflection and transmission parameters of the structure. These parameters also validates the absorption characteristics of the structure. The performance of the fabricated structure for different polarization and angle of incidence is measured and the results are in good agreement with simulation. Finally, the use of this structure to reduce the RCS of a patch antenna is demonstrated. (paper)