Strong and wide microwave absorption of multilayered metastructure enhanced by impedance matching mechanism

The present study proposes a strong and wide microwave absorption of multilayered metastructure (SWMAMM) capable of achieving an ultra-wideband absorption of -20 dB and 60 degrees oblique incidence. SWMAMM primarily consists of metasurface-I (MS-I), metasurface-II (MS-II), and a top absorption-enhanced skin, which are separated by three support dielectric slabs. Based on impedance matching theory and the interference model, MS-I serves as the core functional layer for wideband absorption; whereas MS-II not only provides ultra-wideband impedance matching but also enhances absorptivity, distinguishing it from most designs. To further improve impedance matching, different hole arrays are incorporated into the substrates of MS-I, MS-II, and the top absorptionenhanced skin by modifying their equivalent reactance. The measurement results demonstrate that the -10 dB and -20 dB reflection bands are separately in the range of 3.97-23.19 GHz and 5.24-21.81 GHz when the oblique incidence angle reaches 5 degrees; the -10 dB reflection band can cover the range of 5.99-25.00 GHz when the oblique incidence angle reaches 60 degrees. Our approach, which involves impedance matching design of MS-II and optimizing impedance matching by incorporating different hole arrays into the substrates of the MS-I, MS-II, and the top absorption-enhanced skin, can be applied to various unit cells and dielectric materials. This approach offers significantly enhanced convenience and efficiency compared to existing designs, thereby facilitating further optimization and development of Electromagnetic absorbers.