Equivalent circuit model of an ultra-thin polarization-independent triple band metamaterial absorber

This paper presents equivalent circuit modeling of an ultra-thin polarization-independent metamaterial microwave absorber consisting of three concentric closed ring resonators (CRR). The unit cell size as well as the other geometrical dimensions like radii and widths of the rings are optimized so that absorptions take place at three distinct frequencies near to the middle of the FCC defined radar spectrum eg., at 5.50 GHz, 9.52 GHz and 13.80 GHz with peak absorptivities of 94.1%, 99.6% and 99.4% respectively. The equivalent circuit model of the triple band absorber has been developed sequentially considering the single band and double band absorber models. The circuit simulation of the final model agrees well with the full-wave simulation, thus validating the modeling technique. The structure is also fabricated and experimental absorption peaks are found close to the simulated values.