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FINITE ELEMENT ANALYSIS OF CMUTs: CONVENTIONAL VS. COLLAPSE OPERATION MODES

2006-01-01
Yaralioglu, Goksen G.
Bayram, Barış
Khuri-Yakub, Butrus T.
Collapse mode has been proposed to improve Capacitive Micromachined Ultrasonic Transducer (CMUT) performance in terms of output pressure and receive sensitivity. The focus of this study is to compare the performance of optimized designs for conventional and collapse mode operations using finite element analysis (FEA). For this purpose, we have developed a 2D finite element model for output pressure calculation of CMUTs using commercially available FEA software (ANSYS 10.0). The model is composed of a membrane, a fluid waveguide and an electrical port. The membrane and the fluid part are constructed using axisymmetric plane elements. The electrical port is added to the model by using transducer elements that are already available in ANSYS. Through transient analysis non-linear calculations are performed and average output pressure over the membrane surface is calculated for a given electrical excitation that is applied to the electrical port. First, the effect of various transducer parameters such as radius, thickness, bias voltage, are investigated for conventional mode. Then, the performance of membranes operating in different modes are compared. The parameters of the membranes are selected such that their center frequencies and the collapse voltages match for a fair comparison of transducer performance. Our calculations show that the membrane operating in conventional mode required 100 Vpp AC amplitude for 2 MPa peak-to-peak output pressure whereas 38 Vpp AC excitation generated the same output pressure for collapse mode membrane. In addition, we have compared the second harmonic levels generated by the both designs. For 2MPa peak-to-peak output, the second harmonic amplitude is found to be 13.5 dB below the fundamental for conventional mode design. However, the second harmonic amplitude is -12.0 dB for the collapse mode design.