Wide-angle broadband microwave metamaterial absorber with octave bandwidth

In this study, a broadband metamaterial absorber is presented with octave bandwidth for practical applications. The unit-cell of proposed absorber structure consists of simple geometrical patches placed diagonally on the top surface of the structure. The proposed structure exhibits broadband absorption response of 8.30 GHz from 6.86 to 15.16 GHz covering the entire X-band with more than 90% absorptivity. Three distinct absorption peaks at 7.24, 10.18 and 14.32 GHz have been observed in the absorption spectra. The roles of the geometrical parameters have been investigated to explain the principle of absorption. The structure is studied under oblique incidence for both transverse electric and transverse magnetic polarisations, where the broadband response holds good up to 45 degrees incident angles in both the cases. Owing to the two-fold symmetry, the structure is sensitive to polarisation of the incident field exhibiting maximum absorption at 0 degrees and 90 degrees with no absorption taking place at 45 degrees angle of polarisation. The structure is fabricated and the experimental results are in good agreement with the simulated responses. The proposed structure is very thin (similar to lambda/8.5 with respect to the centre frequency of the bandwidth) compared with the commercially available microwave absorbers.