Dual-band Flexible Metamaterial Absorber Working in 5G Band

This article presents a thin and flexible artificial electromagnetic absorber with two absorption peaks at frequencies of 28 and 39 GHz for 5G communication. Copper and a flexible FR4 substrate are used in a pyramid-shaped layered configuration, achieving absorption rates exceeding 99% at 28 and 39 GHz. The thickness of the proposed structure is only 0.34 mm, which is ∼1/32 and 1/23 of the corresponding free-space wavelengths at the absorption frequencies. Due to its symmetric structure, the absorber is polarization-insensitive. Furthermore, the proposed structure exhibits over 90% absorption within the incident angle range of −45° to 45°. To investigate its absorption mechanism, the electric field and magnetic field distributions at the absorption frequencies were analyzed. Then a 150 × 150 mm2 sample was fabricated using printed circuit board manufacturing techniques. This sample was placed on flat or curved surfaces and tested under normal or oblique incidences. The experimental results were consistent with the simulated results, confirming the feasibility of the design. This absorber can be applied in 5G communication and millimeter-wave imaging.