Metamaterial absorbers (MMA) are electromagnetic absorbers based on metamaterials, which are artificial materials engineered to attain bulk electromagnetic properties not readily found in nature. In the RADAERO project, ultra-thin and ultralight MMAs are developed in the X-band, suitable for aviation applications, such as RCS reduction of UAVs. The MMA's uniplanar form and light weight ensure that the airworthiness and structural integrity of the UAV are not degraded. A uniform MMA is designed by arranging resistive (Rs = 1Ohm/sq) aluminum patches of submicron thickness (~100nm) on an ultra-thin (h=0.27mm) and flexible metal-backed Polyethylene Terephthalate (PET) substrate. A non-uniform 3X3 MMA is systematically synthesized by a semi-analytical approach based on surface impedances to enhance the performance of the uniform MMA. The non-uniform MMA achieves broadband and polarization-insensitive absorption and is suitable for the UAVs’ curved surfaces.

The key innovative aspects of the RADAERO MMAs are:

- ultra-thin and ultralight implementation with a thickness close to 1/100 of the operating wavelength,

- uniplanar and flexible form that renders them suitable for curved UAV surfaces,

- broadband performance of the non-uniform MMA, close to that dictated by Rozanov’s limit.