Constitution Method for Broadband Acoustic Metamaterials Based on the Design Theory of a One-Dimensional Distributed Transmission-Line Model

A method for realizing broadband acoustic metasurfaces composed of a one-dimensional distributed transmission-line model is proposed. There are no design formulas for determining the structural parameters of the structure constituting acoustic metasurfaces in the conventional method, and therefore parameter extractions by means of many calculations with numerical simulations are needed to realize acoustic metasurfaces. There are also narrow band operations or impedance matching problems. On the other hand, this paper shows that we can design broadband acoustic metasurfaces by determining the structural parameters with the design formulas of the model without many calculations. An acoustic metasurface that refracts incident plane waves at an angle of 20 degrees is first designed by using one-dimensional meander acoustic waveguide structures equivalent to the model, and these structural parameters are determined by the design formulas of the model and the modifications of the error from the theory. Full-wave simulations are performed, and the broadband operations and the validity of the design theory are shown from these results. Furthermore, a broadband acoustic flat lens is designed with the proposed structures as an example of the application of the proposed method, and these operations are also demonstrated by similar full-wave simulations.