Novel Local-Chiral Metamaterial: Effective Modulation of Amplitude & Phase for Wideband Polarization-Insensitive Absorption.

Metamaterial has received widespread research in the fields of electromagnetic stealth due to its characteristics of strong resonance and flexible designability. However, a lack of a comprehensive understanding of the internal physical mechanism still imposes certain limitations on broadband absorption designs. Hence, this work proposes a new strategy for the broadening of the working frequency band of metamaterial absorbers by constructing local-chiral features to regulate the amplitude and phase information. The absorber consists of staggered cut-wire metal patterns with lumped resistors placed at the center position determined by characteristic mode analysis. Combining the modal significance, equivalent circuit, surface current, electric field distribution, and symmetry model theory, the working mechanism for wideband absorption performance has been analyzed in detail. The experimental results are in good agreement with the simulation results; the absorption rate exceeds 82% in the frequency range of 4.5-11.7 GHz and surpasses about 90% in the frequency range of 4.7-10.8 GHz under transverse electric (TE) or transverse-magnetic (TM) polarizations. Compared to the case without chiral features, the proposed design can achieve a 28% increase in operating bandwidth. The proposed design method is applicable for the optimization of various typical dipole-type metamaterial absorbers and provides a novel strategy for future wideband metamaterial absorption.