Matching Networks Design for Ultrasonic Guided Wave Interdigital Transducers

Ultrasonic guided waves interdigital transducers realized with piezoelectric materials are of interests for Structural Health Monitoring systems because their capability of Lamb wave mode selection respect to single element transducers. Besides this advantage the coverage of large areas with minimum number of elements is an important challenge and the problem of efficient excitation with integrated electronics must be solved. This work proposes an electrical matching network topology made of L and C passive components that can be designed for the tradeoff between electrical to mechanical conversion efficiency and bandwidth. The network circuit is analyzed considering the equivalents transducer impedance and the output impedance of the driving electronics. The design rules derived by the transfer function analysis are described and a case study for a piezopolymer IDT is presented. Finally with the implementation of the integrated matching network with the connector of the IDT the effect of cable capacitance is minimized. In conclusion the article is a contribution for using IDT efficiently and in a versatile mode for different electronic front-ends that usually operate at low power supply voltage.