Comment on "A novel ultrathin and broadband microwave metamaterial absorber" [J. Appl. Phys. 116, 094504 (2014)].

In a recent article, Wang et al. [J. Appl. Phys. 116, 094504 (2014)] proposed an ultra-thin broadand microwave metamaterial absorber and claimed the absorption above 90 % in the operating band of 8.85 GHz–14.17 GHz. In this comment, we argue that the authors have neglected the cross-polarized reflection in their calculation of absorption. The proclaimed anisotropic pentagon patch metamaterial is predominantly a cross polarizer for the normally incident electromagnetic wave. We demonstrate that the actual absorption of the metamaterial structure remain less than 40 %. Hence, the proposed metamaterial is not a perfect broadband absorber; however, it can be used as an efficient cross-polarizer. [ABSTRACT FROM AUTHOR]