A flexible ultra-broadband multi-layered absorber working at 2 GHz-40 GHz printed by resistive ink

A flexible extra broadband metamaterial absorber (MMA) stacked with five layers working at 2 GHz-40 GHz is investigated. Each layer is composed of polyvinyl chloride (PVC), polyimide (PI), and a frequency selective surface (FSS), which is printed on PI using conductive ink. To investigate this absorber, both one-dimensional analogous circuit analysis and three-dimensional full-wave simulation based on a physical model are provided. Various crucial electromagnetic properties, such as absorption, effective impedance, complex permittivity and permeability, electric current distribution and magnetic field distribution at resonant peak points, are studied in detail. Analysis shows that the working frequency of this absorber covers entire S, C, X, Ku, K and Ka bands with a minimum thickness of 0.098 lambda max (lambda max is the maximum wavelength in the absorption band), and the fractional bandwidth (FBW) reaches 181.1%. Moreover, the reflection coefficient is less than -10 dB at 1.998 GHz-40.056 GHz at normal incidence, and the absorptivity of the plane wave is greater than 80% when the incident angle is smaller than 50 degrees. Furthermore, the proposed absorber is experimentally validated, and the experimental results show good agreement with the simulation results, which demonstrates the potential applicability of this absorber at 2 GHz-40 GHz.