Layered Piezoelectric Transducers

摘要

The subject of this article is layered ('sandwich') piezoelectric transducerswhich are layered acoustic lines whose basic component is a piezoelectric sensitive element which excites the line to resonance oscillations. The authors discuss different designs of sandwich transducers and the modes which occur in them. The authors analyze the effect of the position of the piezoelectric sensitive element on the performance of the transducer. The authors also present functions which describe electrical and mechanical losses in the transducer, electrical and mechanical power constraints, the electromechanical coupling coefficient, and the ultrasound energy emitted to the environment. The authors discuss the role of initial stress and the changes it induces in the characteristics of the ceramic. The authors calculated and measured radiation resistance for different designs and obtained quite consistent results. The results of measurements of such parameters as the resonance frequency, the electromechanical coupling coefficient, radiation resistance, and efficiency taken at the Acoustoelectronics Laboratory for transducers of different designs and sizes are given.