超音波換能器匹配層之研析

Analysis of Ultrasonic Transducer Matching Layer

林冠宇(Guan-Yu Lin)

指導教授 ： 宋家驥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02392

摘要

本文重點在探討超音波換能器中與介質聲學阻抗的匹配層。利用壓電片波動方程式與梅森等效電路當作設計概念，推導出壓電換能器的阻抗矩陣，為了簡化阻抗矩陣求解時複雜的邊界條件的計算，將聲波能量傳遞的觀念來分析換能器內部結構，進而推導出換能器的傳輸矩陣，並用來模擬換能器結構向內外傳遞的聲波能量，以傳輸矩陣模擬換能器輸出聲波訊號，可將其等同為換能器的靈敏度，討論不同厚度的匹配層對於結構振動的影響。
　　本研究透過模擬來找到換能器中不同匹配層厚度對轉換函數影響的趨勢；接著在實驗室中自行製造換能器，利用脈衝回波系統量測換能器的靈敏度，找出換能器中不同匹配層厚度的靈敏度趨勢，結果顯示，模擬與實作的趨勢上相近，但能量的峰值上有些誤差，再改善製作流程與排除壓電片本身靈敏度不同等原因，重新製造三組不同匹配層厚度的換能器，並重新比較其趨勢，最終模擬與實驗的趨勢吻合。
　　在硬體設備上利用固定機構將換能器與反射板的距離固定，讓所有換能器量測時都位在同一個水平上，在配合脈衝收發器與數位示波器進行量測，以確保實驗的可信度。此外還製作隔離發射訊號與接收訊號的電路，避免發射與接收的訊號互相干擾，造成量測能量上的誤差。

關鍵字

超音波換能器 ； 匹配層 ； 阻抗矩陣 ； 傳輸矩陣 ； 靈敏度

並列摘要

The aim of this paper is to explore the sensitivity of ultrasonic transducer front matching layer using the piezoelectric wave equation and mason equivalent circuit as design conceptions. First, we introduce the structure of the ultrasonic piezoelectric transducer and the factors that impact the performance of the transducer. Through the wave equation, the impedance matrix of piezoelectric transducer is derived. In reproduction order to simplify the complex boundary condition on impedance matrix, using the concept of the acoustic energy transmitted to analyze the internal structure of the transducer. Then, the transfer matrix of transducer is derived. It can simulate acoustic signal transmission matrix transducer which are transferred by layers of the structure inner and outer to affect transducer transfer function. So, we can regard the transfer function as the sensitivity of transducer.
　This study found the tendency in different thickness of matching layer on impact of transfer function through the simulation. Using the pulse-echo system to measure the sensitivity of each transducer, and also find their tendency. The result shows the tendency of simulation is similar to experiment, but the peak value of sensitivity is not match. Also trying to improve the process to reproduce the different thickness of transducers and compare with each tendency. Finally, both are match.

並列關鍵字

Ultrasonic transducer ； matching layer ； impedance matrix ； transfer matrix ； sensitivity

參考文獻

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