Research On The PT-Symmetric Thin Plate Based On Shunt Piezoelectric For Negative Refraction And A Retroreflector Based On Diffraction Theory

This paper contains two parts.In the first part,we study how to realize negative refraction of elastic plate waves by using a PT-symmetric structure.Compared with the negative refraction of a wave realized by a phononic crystal or a metamaterial,the negative refraction based on the PT-symmetric has the advantages of simple structure and adjustable frequency.To obtain the adjustable loss and gain,we connected the shunt circuit with series inductance and positive/negative resistance on the piezoelectric unit,and realized the loss and gain of elastic wave through electric resonance.In order to obtain the structural parameters of PT-symmetric elements under the conditions of negative refraction,the scattering matrix method is used to study the transmission properties of the system,and the relationship between the properties of the wave field and the structural parameters of the system is obtained.The design and methods in this paper provide new ideas for the research of PT-symmetric structures.In the second part of this paper,the design method of perfect metasurface is discussed,and an acoustic retroreflector based on grooved planar plate is proposed.Different from the principle of gradient metasurface,the retroreflector is designed by grating diffraction theory.The three-angle and five-angle retroreflector of acoustic wave are realized.The finite element simulation results show that the efficiency of the retroreflector is close to 100%.