Dependence of functional mechanism of matching layer on excitation signal type for ultrasonic transducers-2

Abstract

Acoustic matching layers are widely employed in high-frequency transducers which are excited by different signal types depending on applications. In this study, a theoretical method has been proposed to investigate the dependence of functional mechanism of matching layer on excitation signal types, i.e., short pulse and long pulse. The results indicate that the matching layer acts as a bandpass frequency filter under the two excitation signal types. In the short pulse excitation case, the matching layer can improve bandwidth and transmitting voltage response simultaneously, whereas for the case of long pulse excitation, the increased bandwidth is at the expense of transmitting voltage response. To verify our theoretical results, underwater acoustic transducers with and without matching layer were fabricated and tested. The thickness design principle of matching layer was modified due to the frequency-dependent acoustic radiation impedance. The experimental results verified the theoretical prediction. Our results provide a deep insight into the fundamental principle of matching layer design according to practical applications.