Ultrathin S-Band Multifunctional Metamaterial with Broadband Microwave Absorption and Hydrophobic Characteristics

Effective absorption in the S-band usually requires relatively thick absorbing materials. However, growing application demands necessitate the development of high-performance materials with subwavelength thickness. This study presents a broadband absorbing metamaterial for the S-band, based on a novel structural design featuring a nested hexagonal metal resonant layer integrated with a carbonyl iron powder (CIP)/charcoal (CH)/epoxy resin (ER) composite slab. This structural innovation enables exceptional S-band absorption within a subwavelength thickness, effectively overcoming the inherent physical limitations of traditional materials. By combining the arch measurement method and simulations over the 2–18 GHz, we demonstrate that the metal resonant layer of the metamaterial plays a key role in controlling the electromagnetic field vector distribution. This work investigates the mechanism for enhancing S-band absorption in metamaterials through the redistribution of electromagnetic field vectors. Additionally, magnetic loss from CIP/CH/ER and dielectric loss from the resonators further enhance absorption performance. The designed absorbing metamaterial exhibits effective absorption at a thickness of only 2.25 mm, with a reflection loss (RL) below −10 dB from 2.2 to 3.8 GHz. Simultaneously, it can maintain a radar cross-section (RCS) below −10 dBm2 in a wide-angle range of ±160°. Furthermore, a superhydrophobic coating with a contact angle of 152° was prepared for absorbing metamaterial. This coating allowed the metamaterial to preserve its microwave absorption performance while imparting self-cleaning capability. This study proposes a multifunctional absorbing metamaterial for efficient absorption in the S-band.