Multilayer Stairstep Piezoelectric Structure Design for Ultrabroad-Bandwidth Ultrasonic Transducer

In order to obtain an ultrasonic transducer (UT) with ultra-broad bandwidth (BW), a multilayer stairstep piezoelectric structure (MSPS) is designed and fabricated. Based on the theoretical computation, the relationship between the resonant frequency and thickness of the piezoelectric layer is obtained. The designed MSPS includes 15 layers from center to side, and its frequency range is 5-22 MHz. The finite element method (FEM) based PZFlex software is used to predict the performance of UT with the designed MSPS, and the thickness of each layer is optimized according to the simulation results to achieve the ultra-broad-BW UT. The UT with the designed MSPS is fabricated and systematically characterized. The measured results show that the fabricated UT has a center frequency of 10.54 MHz and a -6 dB BW of 121%, which agree well with the simulation results (11.75 MHz and 140%). The MSPS has significant potential in UT applications.