Inserting an impedance matching layer between different materials is the most straightforward and common method which can significantly reduce the reflection at the interface. Given the extensive variety of materials, the fixed impedance distribution of the matching layers seriously limits the application of the matching layer.

Researchers from the Institute of Acoustics of the Chinese Academy of Sciences (IACAS) and Jishou University designed and fabricated a tunable gradient impedance matching layer (TGIML) to eliminate the impedance step.

The TGIML was composed of periodical piezoelectric disks with shunting capacitors. Through the elaborate modulation of the shunted capacitors, the proposed TGIML could adapt interfaces formed by different materials. Two interfaces formed by solid rods were constructed to demonstrate the performance of the TGIML. The simulated and experimental results verified that, after inserting the TGIML, the transmission could be enhanced significantly in a wide frequency range for both interfaces.

It is believed that the proposed TGIML has great potential for wide applications in the development of ultrasound transducers, nondestructive testing and energy harvesting.

The research, published online in Journal of Applied Physics, was supported by the National Natural Science Foundation of China.

Figure 1. Photo of the interface part of the TGIML experimental system. (Image by IACAS)

Figure 2. Measured transmission spectrums normalized by the transmission spectrums without TGIML for the interface formed by (a) steel rod/ polymethyl methacrylate rod and (b) steel rod/aluminum rod. (Image by IACAS) 

Reference:

Wu Jien, YANG Yuzhen, JIA Han, XU Xiangyuan, YANG Jun, HE Zhaojian, DENG Ke. A tunable gradient impedance matching layer based on piezoelectric materials with external circuits. Journal of Applied Physics 2020, 128, 064502. DOI: 10.1063/5.0012536.

Contact:

ZHOU Wenjia

Institute of Acoustics, Chinese Academy of Sciences, 100190 Beijing, China

E-mail: media@mail.ioa.ac.cn