Metal Piezoelectric Ceramic Cross Porcelain Double Composite Bending Vibration Transducer

Because the specific acoustic impedance of transducer doesn't match withair's, Air-couple transducer hasn't been developed very well for a long time. ToTransducer and air, it's so difficult for impedance to math, so the radiation efficiency ofair-couple transducer was very low, in other word, it limited to use in practice. Today,people have two methods on impedance matching: First, by using the matching layer ofhalf wavelength, the radiation efficiency of air-couple transducer was improved. Second,by using flexural vibration mode, the difficult on imnpedane match was resolved in somedegree. The metal-piezoelectric composite air-couple tranducer was developed on thebase of piezoelectric-telephone transmitter. The transducer has an advantage of simplestructure, sealing with ease, low electtic-impedance ed mechbocal-impedance, easilymatching with circuit and medium, easily extending bandwidth, stable and so on. Butstudying reference on this transducer was only paid attenion to base-frequency. In thespaper, the metal-piezoelectric composite air-couple transducer was systemically studiedby the writer, and the designtw methods were given.(l) With the variations approach, frequencies equation of its first and second modewere derived, so did Keff In experiment, frequency equation associated with shape-parameter was verified. The conclusion is in good agreement with experiment.(2) The eXpression of directivity of far field and near field was derived. Theradiation direchvity and near-field changing are simulated by computer, which are ingood agreement with principle of reference.(3) The kinetic energy of composite transducer is obtained by using the methd ofenergy. The expression of equivalent mass can be obtaned from the kinetic energy, andthe equivalent capacitance from the equivalent mass.(4) The radiative imPedance on comPosite transducer was derived. The curve ofthe radiative-impedance associated with shaPe-parameter was given. ComParin theconclusion with the principle, the conclusion is agreement with the PrinciPle.