Array Equivalent Circuit Model and Experimental Analysis of Square CMUTs

The equivalent circuit is a commonly used tool for performance analysis during capacitive micromachined ultrasonic transducer (CMUT) design and optimization. In this study, the immersion equivalent circuit model of a square CMUT array is established for the first time. Using this model, the vibration, electrical, and acoustic characteristics of square CMUTs can be rapidly analyzed. Consequently, it can replace the time-consuming finite element model (FEM) for design and optimization. For comparison with the equivalent circuit model presented in this article, the FEM of the square CMUT array was established by COMSOL 6.0a. The theoretical calculation results of the equivalent circuit model are highly consistent with the FEM results. Finally, a $28\times 28$ CMUT array composed of square cells was fabricated using the wafer bonding process, and its vibration and impedance characteristics were tested using a Laser Doppler Vibrometer and an impedance analyzer. All experimental results well verified the accuracy of the proposed equivalent circuit models.