Theoretical Modeling and Equivalent Electric Circuit of a Bimorph Piezoelectric Micromachined Ultrasonic Transducer
Theoretical Modeling and Equivalent Electric Circuit of a Bimorph Piezoelectric Micromachined Ultrasonic Transducer
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DOI：
10.1109/tuffc.2012.2284
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发表时间：
2012-05-01
影响因子：
3.6
通讯作者：
Kim, Sang-Gook
中科院分区：
文献类型：
--
作者：
Sammoura, Firas;Kim, Sang-Gook
首次建立了圆形双压电微机械超声换能器的电路模型。该模型由一个电子网格组成，通过一个变压器元件耦合到一个机械网格上。双压片PMUT由两个相同材料的压电层组成，厚度相等，夹在三个薄电极之间。具有相同极化轴的压电层被偏置相同大小但相反极性的电势。由逆压电效应造成的两层之间的应变不匹配导致薄膜振动，从而传递压力波。当接收到声波的回波时，由于直接的压电现象，薄膜变形导致电荷的产生。用两个正则方程描述了膜角速度和电流与外加电场、入射声压和膜边缘力矩之间的关系。从电学域到力学域的转换系数是双向的，系统是可逆的。提取了模型的电路参数，包括变压器比、钳位阻抗、弹簧软化阻抗和开路机械阻抗。通过产生空气和水负载条件下的输入阻抗和平均板位移随频率的变化曲线，对理论模型进行了全面的检验。研究了由含损耗介质的压电材料组成的PMUT，并计算了其最大可能的电声转换效率。
An electric circuit model for a circular bimorph piezoelectric micromachined ultrasonic transducer (PMUT) was developed for the first time. The model was made up of an electric mesh, which was coupled to a mechanical mesh via a transformer element. The bimorph PMUT consisted of two piezoelectric layers of the same material, having equal thicknesses, and sandwiched between three thin electrodes. The piezoelectric layers, having the same poling axis, were biased with electric potentials of the same magnitude but opposite polarity. The strain mismatches between the two layers created by the converse piezoelectric effect caused the membrane to vibrate and, hence, transmit a pressure wave. Upon receiving the echo of the acoustic wave, the membrane deformation led to the generation of electric charges as a result of the direct piezoelectric phenomenon. The membrane angular velocity and electric current were related to the applied electric field, the impinging acoustic pressure, and the moment at the edge of the membrane using two canonical equations. The transduction coefficients from the electrical to the mechanical domain and vice-versa were shown to be bilateral and the system was shown to be reversible. The circuit parameters of the derived model were extracted, including the transformer ratio, the clamped electric impedance, the spring-softening impedance, and the open-circuit mechanical impedance. The theoretical model was fully examined by generating the electrical input impedance and average plate displacement curves versus frequency under both air and water loading conditions. A PMUT composed of piezoelectric material with a lossy dielectric was also investigated and the maximum possible electroacoustical conversion efficiency was calculated.