中文摘要：

研究了一种具有多个共振频率的矩形辐射器夹心式超声换能器，换能器由圆柱形后盖板、压电陶瓷晶堆及矩形六面体辐射器前盖板组合而成。利用表观弹性法和一维近似理论给出了多频换能器横向及纵向理论共振频率方程。对一种特殊情况下的此类换能器进行了有限元及实验分析，给出了各自的频率输入导纳曲线。对理论和实验结果进行分析后表明，此类矩形辐射器夹心式超声换能器可以在不同的振动模态上工作，具有多个共振频率．

英文摘要：

A new kind of multi frequency transducer with a rectangular radiator is analyzed in this paper. The transducer consists of metal cylinder, piezoelectric ceramic pile and rectangular radiator. The fundamental modes of the coupled vibration of rectangular radiator are analyzed, and the frequency equations of the fundamental modes in the transverse directions are given by means of the apparent elasticity method. Meantime, based on the one dimensional longitudinal vibration theory, the resonance frequency equation in longitudinal direction of the multi- frequency ultrasonic transducer is derived out. One ultrasonic transducer of this kind is designed and simulated by finite element method, and modal shapes and harmonic response are analyzed. The ultrasonic transducer is also designed and manufactured. The resonance frequencies are measured and compared with the theoretical results. It is shown experimentally and theoretically that the compound multi-frequency ultrasonic transducer has two resonance frequencies.