Acoustic Impedance Matching of PMN-PT/epoxy 1-3 Composites for Underwater Transducers with Usable Bandwidth Restricted by Electrical Power Factor

Volume cost has limited the use of single crystals in underwater applications, but reported performance of PMN-PT sonar transducers now motivates the design of commercial prototypes. This work addresses optimization of the matching layer for maximum bandwidth of underwater transducers made from PMN-PT/epoxy 1-3 composite plates. Bandwidth is here defined by both the electromechanical transfer function and the electrical power factor. The electrical power factor is the ratio of real to apparent power and must be taken into account for systems with transmitter volt-ampere limitations. PMN-PT single crystals has a higher electromechanical coupling coefficient than commonly used PZT. This requires a lower mechanical quality factor of the transducer design to avoid increased fluctuation of the tuned power factor. For a PMN-PT/epoxy composite with air backing and one matching layer it is challenging to achieve optimum mechanical quality factor, resulting in possible power factor limitation of bandwidth.