Research On Transducer With Broad Beamwidth

The broad beamwidth transducer is one of the most important key technologies of underwater detecting and communication system. According to the demand of broad beamwidth and high power, two kinds of new type transducers are proposed, which are named as'Sandwich Transducer with Composite Horn'and'Transducers with Spherical Stack of Piezoelectric Ceramic'.Sandwich transducer with composite horn combines the advantage of high power of sandwich transducer and the benefits of broad beamwidth of piston like transducer with small emitting area. By introducing the stack of spherical and hemi-spherical structure, transducers with spherica stack can have higher transmitting voltage response for the increasing of the internal electric field intensity. In the meantime, transducers with spherical and hemi-spherical stack can also remain omnidirectional characteristic.First, base on the electro-mechanical equivalent circuit theory, the model of sandwich transducer has been build, and the frequency equation is deduced. Considering the influence of the latten electrodes on the density and the equivalent sound velocity, a modification of this equation is given out using the equivalent parameter theory. Base on the radiation theory of sound wave and the superposition principle of point acoustic source, the directivity of sandwich transducer with composite horn has been deduced. The sandwich transducer can be seen as a piston with finite baffle.The sound pressure on the edge of baffle can be calculated as the piston has an infinite baffle.Then a sphere transducer has been assumed on the edge of baffle. This transducer has a vibration velocity distributed the same as sound pressure distributed of piston. The directivity of transducer can be easily solvent by calculating the directivity of sphere transducer. The data calculated by the model are compared with that by experiments, and the results indicate that the calculation is good agreement with experiment. The frequency equation and the directivity equation have been used to optimize the structure of transducer.Then, the transducer is modeled with Finite Element Method (FEM) in this paper. With the help of modal and harmonic analyzer of ANSYS software, the resonant frequency of the sandwich transducer has been simulated and the electro-acoustic performance of the transducer both in air and under water is analyzed. Furthermore, the effects of the structure parameters on the performance of the transducer are studied.Next, the transducers with spherical stack of piezoelectric ceramic have been studied using the piezoelectric constitutiverelations.The frequency equation has been deduced. And the directivity of sphere transducer with different baffles has been deduced by using the theory of acoustic dipole.The data calculated by the model are compared with experimental data, and they match well.Finally, the fabricating technics for transducers with broad beamwidth are studied, and the process flow is established. Prototypes of these two kinds of transducers are designed and fabricated. The experimental results show these two kinds of prototypes have the advantages of broad beamwidth and high power.