A quad-band metamaterial microwave absorber based on elliptical and square ring resonators

The development of wireless communication has grown interest in the high-performance microwave-absorbing materials. This paper presents the design of a quad-band metamaterial absorber based on a hybrid resonator integrating elliptical and square rings. The unit cell of the absorber consists of a square split-ring resonator, an elliptical SRR, and a square resonant strip, with an FR-4 dielectric substrate and a continuous metallic ground layer at the bottom. Simulation results reveal that this structure achieves near-perfect absorption efficiencies of 99.41%, 99.99%, 99.93%, and 99.25% at the resonant frequencies of 6.41, 11.69, 15.55, and 17.82 GHz, respectively. The analysis of surface current and electric field distributions indicates that each absorption peak arises from distinct mechanisms, including the synergistic interaction between the elliptical ring and the inner resonant strip, as well as the dominant contribution of the external ring resonant structure. Angular response analysis demonstrates that the absorber maintains high absorption efficiency within the oblique incidence range of 0°–45°, exhibiting excellent angular stability. The equivalent circuit of the proposed MMA was designed using ADS software, which demonstrates the designability of the metamaterial absorber. The results were validated by both waveguide and arch reflectivity tests. Compared with previously reported counterparts, the proposed design features a simple configuration, flexible frequency band selection, and high absorption efficiency, thus holding promising application potential in the fields of microwave stealth and electromagnetic protection.