Transfer Matrix Model of Piezoelectric Sandwich Hydrophones

The ultrasonic positioning system in the Jiangmen Underground Neutrino Observatory (JUNO) demands the special hydrophones to sensitively receive the ultrasonic waves in a wide angular range. To meet the requirements of high sensitivity and aimed directivity, a type of piezoelectric sandwich hydrophone (PSH) with a piston head is developed. In this study, the improved transfer matrix method (TMM) is introduced to model the PSH, without omitting the bolt. The impedance matrix of the PSH is generated to reflect the characteristics of each part, and the transfer matrix formulation is built to describe the mechanical relations among the parts of the PSH. The matrix solution method based on the impedance matrix is used to obtain the electroacoustic performance of PSH. The TMM simulations indicate that the effect of the prestressed bolt on the PSH cannot be ignored, especially for the high-frequency transducers. The relevant tests reveal that the TMM can give the effective and accurate estimation for a piezoelectric transducer with the prestressed bolt. The prototypes achieve the maximum sensitivity of -209.3 dB and the beamwidth of 132.2° at the frequency of 143 kHz in water. The PSHs can be used as hydrophones in the JUNO application.