Triple band ultrathin polarization insensitive metamaterial absorber for defense, explosive detection and airborne radar applications

We demonstrate an ultrathin polarization insensitive metamaterial-based Concentric Closed Circular Ring Resonator (CCCRR) perfect absorber for explosive detection, bolometer, indoor radar clear applications, thermal detection, defense applications, airborne and surveillance radar signal absorption applications. The unit cell incorporates three concentric closed circular ring resonators. A parametric optimization has been carried out in order to obtain three discrete absorption peaks at 5.57 GHz, 7.969 GHz, and 13.44 GHz exhibiting absorption intensities of 98.87%, 97.99%, and 99.28%, respectively. Owing to the geometrical symmetry, the structure is polarization insensitive for both TE and TM polarizations and has significant absorbance over a wide angle of incidence of 45 degrees for TE and 75 degrees for TM polarizations. The structure is very compact with physical dimensions of 0.185 lambda o*0.185 lambda o *0.01 lambda o, lambda o is wavelength corresponding to lower absorption peak. The thickness of the proposed structure is lambda o/100, evidencing the ultrathin characteristic of the proposed structure. The insight of absorption mechanism has been illustrated by analyzing the electric field distribution, power loss density, and normalized impedance. An extensive parametric analysis has been exercised to examine the influence of parametric alterations.