Ultra-wide operation band of the high-frequency underwater acoustic transducer realized by two-layer 1–3 piezoelectric composite.

In this paper, the two-layer 1–3 composite transducer using an unconventional part-excitation method is presented to achieve the ultra-wide operation band for the high-frequency underwater devices, in which the part-excitation refers to the method that only the lower-layer is excited, while the upper-layer in contact with the propagation medium is not excited. This method is first proposed by analyzing the longitudinal vibration modes of one piezoelectric rod in the 1–3 composite and finally, we conclude that if the excited lower-layer can be controlled to have thickness given by 3l/2n, where l is the whole thickness of the two-layer rod and n (n > 1) denotes the number of the coupled modes, then first n order modes can be activated simultaneously to form an ultra-wide operation band containing n response peaks. Finite element method (FEM) is employed to investigate the two-layer 1–3 composite with a thickness of 10 mm. The results show that when the thickness of the excited lower-layer is 3 mm (n = 5), the transducer attains the ultra-wideband by coupling five resonances, nearly covering the frequency range from 100 kHz to 1 MHz. According to the difference of response level, the whole band can be divided into multiple local wide bands. A prototype transducer is fabricated based on the FEM results, and the measured results show that the whole band contains three wide bands, covering the frequency ranges 125–295 kHz, 300–480 kHz, and 500–915 kHz, respectively. [ABSTRACT FROM AUTHOR]