EM analysis of metamaterial based radar absorbing structure (RAS) with dual-resonant characteristics

The radar absorbing materials (RAM) and structures (RAS) are widely used in aerospace sectors to reduce the RCS of the aircraft, electromagnetic shielding of high reflection surfaces and metal surfaces etc. The stealth technique is the most typical application of electromagnetic (EM) wave absorption technology. Using this technique, the aircraft and warships can evade detection by reducing their radar cross-section (RCS). Initially, the EM radar absorbers were designed using Salisbury screen (Fnate and McCormack, IEEE APS, 1968; Chambers, Electronics Lett., 1994). This type of absorbers involves the use of resistive sheet and a metallic ground plane to cancel out the reflections from the screen, which may be a disadvantage in stealth technology. The radar absorbing structures are also realized with FSS technology, which provides thin design but shows satisfactory EM performance only at low incidence angle (Singh et al., PIER B, 2012). Recently, introduction of metamaterial technology leads the design of high performance radar absorbers in the frequency range from microwave to terahertz regimes. The permittivity and permeability of metamaterial structure can be controlled by varying the dimensions of its electric and magnetic components. By tuning the resonances of electric and magnetic components, a metamaterial can be impedance-matched to free-space to achieve 100% absorption without using metal plate backing. For instance, in the designing of a metamaterial based absorber, multiple split-ring resonator (SRR) bases with resonant-magnetic inclusion were employed to eliminate the use of metallic backing plates in absorber