Active metamaterials-based coding metasurface for underwater acoustic counterwork

The development of coding metamaterials has enabled flexible digital manipulation of acoustic fields, providing design methodologies for realizing underwater acoustic countermeasures such as acoustic invisibility, acoustic camouflage, and acoustic decoys. In this study, we propose a novel acoustic coding metasurface structure composed of two types of fundamental units with phase responses of 0 and π, arranged according to a 1-bit coding sequence. Based on the comparative analysis theory of acoustoelectric elements, we derived the equivalent parameter representation of an acoustic cavity unit incorporating piezoelectric patches. Furthermore, we designed a digital acoustic unit capable of achieving an acoustic phase delay difference of “π” within a specific frequency range, thereby offering a technical approach for realizing actively switchable digital acoustic metasurfaces. Finite element simulation analysis demonstrates that this coding metasurface based on active acoustic cavities can achieve diverse underwater acoustic countermeasure functionalities through various wavefield control effects.