Multilayer Ultrabroadband Piezocomposite Transducer: Fabrication and Characterization

Abstract

The broad bandwidth is essential for the ultrasonic transducers because of two main reasons: Firstly, the image axial resolution can be improved by broad bandwidth, and secondly, the ultrasound scanning flexibility can be improved by operating the transducer over a wide range of frequencies. Particularly, nonlinear applications such as biomedical imaging that requires transmitting and receiving in different frequencies can utilize broadband characteristics of transducer efficiently. In this study, a dual‐layer piezocomposite transducer was designed by combining two 1–3 piezocomposite transducers with various thicknesses to couple their resonance frequencies and to increase the bandwidth. PZFlex code was used to determine the most promising layer thicknesses for elements of multilayer structure coupling. Finite element analysis showed that the best thickness combination is 1.2 mm and 2 mm. After fabricating multilayer transducers by traditional dice and fill method, their characteristics were examined under water by Labview automated measurement system. Relative sound pressure produced by the transducer was obtained, and their bandwidth was examined at −3 and −6 dB. By varying the individual active layer thicknesses, acoustic impedance of the backing layer and coupling material the best promising broadband transducer design was reported. In addition, ringing characteristics of the transducers were identified by performing the pulse–echo testing. Multilayer transducer with 1.2 mm and 2 mm layer thicknesses and 6 MRayls backing layer gave the best performance in terms of bandwidth and ringing characteristics.