An improved displacement model for micro-electro-mechanical-system based ultrasonic transducer
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This paper analyses the electrical capacitance, electrostatic force on the membrane and displacement profile of a silicon nitride based micromachined ultrasonic transducer. These specified parameters are characterized by a proposed simple and compact fringing field model. The proposed model together with the fringing effect of Landau and Lifschitz method well matches the 3-D simulated PZFlex, finite element method (FEM) extracted results. An equivalent capacitor having electrodes’ diameters comparable to their distance are used in modeling the transmitting transducer. This makes the fringing field at the corners of the electrodes prevalent, resulting in excess capacitive effect. This excess capacitance affects the performance parameters. An observable displacement profile is perceived for variation in device structural and physical parameters. The influences of the device parameters and the bias on the variation of the characteristics of the membrane are also analyzed.
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