Ultrawide Bandwidth and Large-Angle Electromagnetic Wave Absorption Based on Triple-Nested Helix Metamaterial Absorbers

This article presents ultrawide bandwidth (BW) and large-angle helical metamaterial absorbers (HMMAs) consisting of a periodic array of coaxially nested magnetic helices. The enhanced properties of these HMMAs, including ultrawide BW, polarization insensitivity, and wide-angle absorption, are confirmed and illustrated experimentally. Large helix diameter (20–30 mm), small coupling constant (close to 1), and small and large helix nesting (5 and 20 mm) help in the enhancement of the absorption properties. Current distributions and coupling property of these HMMAs are provided, and results reveal that the synergistic effect of the LC resonance and dipole responses of the patterned structure is responsible for the broadband absorption mechanism. HMMAs consisting of a 14 × 14 array of a triple-nested helix exhibit optimal performance. The effective BW with reflection loss below −10 dB (90% attenuation) is up to 27.68 GHz at 8–40 GHz. The HMMAs also show polarization insensitivity in the incident range of 0°–315° and angle insensitivity at all incident angles in the range of 35°–70°. Therefore, our findings here provide a valuable guide to the design and fabrication of chiral MMAs, in particular, the ultrawide BW and large-angle chiral MMAs at microwave or millimeter wave frequencies.