基于扩展BVD模型的压电换能器电匹配研究

Research of Electric Impedance Matching Method of Piezoelectric Ultrasonic Transducer Based on Extended BVD Model

针对提高无损检测压电换能器灵敏度问题,提出了一种电阻抗匹配网络的设计方法。首先通过压电换能器电导纳实验曲线建立压电超声换能器的BVD模型等效电路。根据压电换能器电导纳的实验值对所建立的等效电路进行参数识别,确定等效电路各元件的值;并对参数识别的结果进行理论验证。同时与实验结果进行比对,吻合较好,表明该参数识别的方法可信度较高。在建立等效电路的基础上,采用Smith圆图,基于电匹配理论,设计压电换能器匹配电路;并对匹配后的压电换能器进行理论分析和实验验证。结果表明该匹配电路可将压电换能器的灵敏度提高约三倍。

For improving the sensitivity of piezoelectric ultrasonic transducer,a method for electric impedance matching network was presented. Firstly,a BVD equivalent circuit of piezoelectric ultrasonic transducer is established through the experimental curves of electrical admittance of piezoelectric transducer. The values of each equivalent circuit element are obtained from parameter identification of the equivalent circuit based on the experimental results of electric admittance of piezoelectric transducer and then they were validated theoretically. The results are in good agreement with experiments. It shows that the parameter identification method is with higher reliability. On the basis of equivalent circuit establishment,the matching circuit of piezoelectric transducer is designed with Smith chart based on the theory of electrical matching. Then the matched piezoelectric transducer is analyzed theoretically and verified experimentally. It shows that the sensitivity of piezoelectric transducer can be advanced to about 3 times with this matching circuit.