中文摘要：

超声波换能器已经广泛应用于工业无损检测、医疗诊断等重要领域.同时,随着应用的日益深入,对超声换能器的性能也不断地提出了更高的要求.然而,基于传统的1/4波长匹配技术而制作的超声换能器其带宽等性能已经远远不能满足需求,亟需开发新一代宽带高效的阻抗匹配技术.从非均匀媒质的声波方程出发,首先分析了阻抗按梯度变化媒质的声能量透射,其次探讨了利用变截面管道和分层媒质的方式实现等效的梯度媒质,然后利用有限元软件详细模拟了两至四层匹配的透射性能,已得到了优化的参数.

英文摘要：

Ultrasonic transducers have widely been used in industrial non-destructive detection,medical diagnosis,and other fields of applications.With the development of technology and broadening and deepening applications,there is a constant need of higher performance transducers,e.g.,for higher resolution imagining,etc.To break through the bandwidth limit of traditional ultrasonic transducers that are based on the quarter-wavelength matching,novel impedance matching technology has to be developed.Following the acoustic wave equation in inhomogeneous media, we study the transmission spectrum of continuous media of gradiently varying acoustic properties,and then,explore the possibility of using tubes of variable cross-section and multi-layered media to realize the equivalent gradient media with their matching performance well agreeing with those of the gradient media.Numerical simulations of the performance of transducers with two,three,and four matching layers are conducted by using the finite element method to attain optimized parameters of matching layers.