Tunable prism based on piezoelectric metamaterial for acoustic beam steering

This letter reports a tunable acoustic prism featuring continuous beam steering for transverse waves at a single frequency. The proposed prism is comprised of arrayed piezoelectric unit-cells with individually connected inductive shunt circuits. Taking advantage of wave velocity shifting in the vicinity of the local resonant frequency of unit-cells, we can steer the harmonic transverse wave by adjusting the inductive loads, i.e., tuning the inductances. This beam steering mechanism is facilitated by add-on piezoelectric circuitry through electro-mechanical coupling, whereas the host medium is not altered. Our analysis shows that the propagation direction of an acoustic wave has a tuning range of more than 30 degrees. This tunable prism can be used as an acoustic metamaterial for various devices operating at broadband frequencies.