Abstract
The capacitive micromachined ultrasonic transducer (CMUT), as a new acoustic-electric conversion element, has a promising application prospect. In this paper, the structure of the vacuum capacitive micromachined ultrasonic transducer is presented, and its performance-influencing factors are investigated. Firstly, the influencing factors of the performance parameters of the vacuum CMUT are analyzed theoretically based on the circular plate model and flat plate capacitance model, and the design principles of the structural parameters of the CMUT cell are proposed. Then, the finite element simulation software COMSOL Multiphysics is used to construct CMUT cell models with different membrane materials, membrane shapes, membrane radius thicknesses, and cavity heights for simulation verification. The results show that both the membrane parameters and the cavity heights affect the performance parameters of the Vacuum CMUT. In order to improve the efficiency of the CMUT, materials with low bending stiffness should be selected, and the filling factor of the membrane should be increased. In order to achieve high-transmission sound pressure, a smaller radius thickness and a larger cavity height should be selected. To achieve high reception sensitivity, a larger membrane radius thickness and a smaller cavity height should be selected. In order to obtain high fractional bandwidth, a larger membrane radius thickness should be selected. The results of this paper provide a basis for the design of Vacuum CMUT cell structure.
Highlights
With the development of micro-electro-mechanical systems (MEMS) technology, the capacitive ultrasonic micromachined transducer (CMUT) research has become an important direction of ultrasonic transducer research
The parallel plate capacitance model is usually used to investigate the relationship between the transmission sound pressure and the structure of the Vacuum capacitive micromachined ultrasonic transducer (CMUT) cell [23], coefficient of the membrane, b is the damping coefficient, g is the cavity height, and Vdc as shown in Figure 2, where m and k are the equivalent mass and equivalent spring and Vac are the voltage signals applied to the Vacuum CMUT cell
When the CMUT is in coefficient of the membrane, b is the damping coefficient, g is the cavity height, and Vdc the transmitting state, a DC bias voltage Vdc and an AC excitation voltage Vac are applied and Vac are the voltage signals applied to the Vacuum CMUT cell
Summary
With the development of micro-electro-mechanical systems (MEMS) technology, the capacitive ultrasonic micromachined transducer (CMUT) research has become an important direction of ultrasonic transducer research. Finite element simulation is to construct the geometry, set the boundary conditions and physical field conditions in the finite element simulation software, and use the software’s multi-physics interaction to obtain the performance parameters of the CMUT. This method is simple in modeling and accurate in calculation. This paper mainly analyzes the influencing factors of various performance parameters of the Vacuum CMUT, puts forward the design principles of each structural parameter, and uses the finite element simulation software COMSOL Multiphysics to analyze the influence of the materials, the shape, the radius thickness of the membrane, and the height of the cavity on the performances of vacuum CMUT. The investigation provides a basis for the design and manufacture of Vacuum CMUT
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