Mechanically tunable dual-band metamaterial absorber at ultra-high frequency

We numerically demonstrated a dual-band metamaterial absorber (MPA) operating in low frequency range based on a flexible polyimide substrate. For the flat configuration, two absorption peaks are obtained at 450 MHz and 1.47 GHz with absorption over 90%. The ratios of the periodicity of unit cells and thickness to the longest absorption wavelength are 1/12 and 1/114, respectively. Especially, our MPA is insensitive with polarization and stable with the oblique incidence angle of incoming electromagnetic waves. The proposed MPA maintains an absorption over 90% when incident angle is increased up to 60o. Furthermore, since structure is wrapped and attached to cylindered surfaces (the varying radii from 200 to 500 mm), new absorption peaks can be obtained at higher frequency range. For both flat and curvature states, the absorption mechanism is explained by the magnetic resonance and the perfect impedance matching phenomena.