Dissertation > Industrial Technology > General industrial technology > Acoustic engineering > Ultrasonic Engineering > Ultrasonic transducer

The Study of Electrical Impedanceof Piezoelectric Transducer Based on Transmissionline Theory

Author LiWanChong
Tutor ZhangRui
School Harbin Institute of Technology
Course Condensed Matter Physics
Keywords composite piezoelectric material piezoelectric transducer electrical match transmission-line transformer
Type Master's thesis
Year 2013
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Today, the application of functional materials is more and more wide spreading, the research is very active. The piezoelectric material as one of them attracts a lot of researchers to study them. In recent years, piezoelectric materials are widely used in industry, agriculture, medicine and other fields, particularly in the field of ultrasonic piezoelectric transducer more research. Currently the research on the application of high-performance piezoelectric materials is inadequate, from the majority of scientists concerned more about acoustical matched mechanical aspects. More research on high-frequency electrical matching is needed to be studied to make a breakthrough.To better solve the electrical matching problem, we have designed and fabricated a high-performance prototype1-3composites ultrasonic device, which center frequency is1.3MHz.1-3composite piezoelectric material was used as the piezoelectric vibrator by the transducer design principles. Concerning about the piezoelectric performance of prototype device prepared in this paper, we developed the piezoelectric ultrasonic transducer, which bandwidth is32.9%in a-6dB. Firstly, some work on acoustic matching of piezoelectric ultrasonic transducer is studied to improve the performance of the transducer. Matching layer is prepared by mixing epoxy resin and alumina powder, which thickness is0.53mm, By this way, the ultrasonic transducer sensitivity was increased by3.41dB, and the bandwidth of ultrasonic transducer in-6dB increased to45.6%, compared with unmatched ultrasonic transducer. This paper focuses on the theory and method of electricity matching. It is the first time to accurately research impedance matching using the transmission line transformer. The method to select exact parameters and the specific process approach of the transmission line transform were studied. The performance of this1-3type piezoelectric ultrasonic transducer is measured by using the transducer spontaneous admission mode under electrical matching conditions. The results show that the sensitivity of the transducer increases by11.1dB, the transducer bandwidth increase from32.9%to38.2%at-6dB after electrical matching. This suggests sensitivity of the transducer can extremely improve by using transmission line transformer to realize electrical matching. Electrical matching realized by using transmission line transformer is also helpful to increase the bandwidth of transducer. Finally, after the acoustic and electrical matching, the result shows that the sensitivity of the transducer increases by14.2dB, and the bandwidth increase from32.9%to53.8%in-6dB, comparing with the unmatched transducer. This study provides a precise and specific electrical matching method for improving the matching performance of the transducer, especially for fabricate high performance piezoelectric ultrasonic transducer.

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