Equivalent Circuit Model of Circular CMUT With Partially Covered Center Electrode

The capacitive micromechanical ultrasonic transducer (CMUT) has several advantages, including a compact size, high precision, and a high electromechanical coupling coefficient, making it widely utilized in flow detection, ultrasonic imaging, biochemical material detection, and other applications. To effectively capture these remarkable advantages, an equivalent circuit model is frequently established to analyze the fundamental performance characteristics of the CMUT. In this manuscript, the immersion equivalent circuit model of the partially center electrode-covered circular CMUT (PCEC-CMUTs) is established. Based on the established model, the vibration, electrical, and acoustic characteristics of the PCEC-CMUTs can be rapidly and accurately determined. Concurrently, a finite element model (FEM) is developed using COMSOL 6.0a to verify the accuracy of the established model and ensure computational precision. The average vibration velocity, resonant frequency, impedance characteristics, and output pressure distribution showed excellent agreement, further validating the accuracy of the theoretical model. When the electrode coverage ratio (Mr) varies within the range of 0.1 to 0.9 and the bias voltage percentage changes between 10% and 90%, the relative error of the resonant frequency remains below 5%.