High-frequency Broadband Underwater Acoustic Transducer Based On 1-3 Relaxor Ferroelectric Single Crystals

Underwater transducers are the window of information communication between sonar system and water medium,they behave as the ears and eyes in terms of target detection and positioning.To solve the challenge of detection and precise imaging of small target,the high-frequency underwater acoustic transducers with broadband and high transmitting voltage response/sensitivity were investigated.Pb(Mg_1/3Nb_2/3)O₃-0.32 Pb Ti O₃relaxer ferroelectric single crystal which possesses high piezoelectric constant was selected as piezoelectric material,then,the transducers were integrated by 1-3 relaxor ferroelectric single crystal composites,matching layers and backing,respectively.However,it is noted that the design of matching layers and backing for high-frequency underwater acoustic transducers is different from that of medical and non-destructive transducer owing to the working scenario.Firstly,the KLM(Krimholtz,Leedom and Matthaei)equivalent circuit has been employed to investigate the dependence of functional mechanism of matching layer on excitation signal types,i.e.,short pulse and long pulse.Then the matching layer parameters were designed by taking account into the frequency-dependent acoustic radiation field in the water.Secondly,the optimization of backing parameters was conducted,e.g.characteristic impedance and mechanical loss,etc.Finally,to verify the theory predictions,prototype transducers composing of 1-3 piezoelectric composites,matching layers and backing were fabricated and tested.The results indicate that the matching layer can improve bandwidth and transmitting voltage response simultaneously under short pulse excitation,whereas for the case of long pulse excitation,the increased bandwidth is at the expense of transmitting voltage response.Besides,it shows that the mechanical loss of the backing plays important role on the fluctuation of transmitting response curve,besides the it is found that the characteristic impedance of backing mainly effect the low frequency range of transmitting response curves.In addition,the experimental results of transmitting voltage response agreed well with the theoretical ones.Our results provide a deep insight into the fundamental principle of matching layer and backing design according to practical applications.