Low-profile broadband microwave absorber based on magnetic coating and artificial electromagnetic structures

In order to realize electromagnetic stealth of large equipment, we propose a low-cost, mass-producible composite microwave absorber in this paper. The developed novel EM absorber comprises a pattern-impregnated honeycomb structure with the absorbent of carbon black (CB), a resistive frequency selective surface (FSS) embedded in polypropylene (PP) foam, and a mixture coating covered on a metal plane whose absorbent is flaky carbonyl iron (FCI). CB particles and FCI particles provide electrical and magnetic losses at the microscopic scale. Moreover, the subwavelength-scale artificial electromagnetic structure achieves broadband matching to free space by adjusting macroscopic geometric parameters. The consistency between measurements and simulations proves that the composite absorber achieves over 90% absorption ratio with a thickness of 8.3 mm from 2.06 to 18 GHz (corresponding to a fractional bandwidth of 158.9%). Additionally, this composite absorber possesses good mechanical property with a maximum uniaxial tensile stress of 67.43 MPa.