Square diaphragm CMUT capacitance calculation using a new deflection shape function

A new highly accurate closed-form capacitance calculation model has been developed to calculate the capacitance of capacitive micromachined ultrasonic transducers (cmuts) built with square diaphragms. the model has been developed by using a two-dimensional polynomial function that more accurately predicts the deflection curve of a square diaphragm deformed under the influence of a uniform external pressure and also takes account of the fringing field capacitances. the model has been verified by comparing the model-predicted deflection profiles and capacitance values with experimental results published elsewhere and finite element analysis (fea) carried out by the authors for different material properties,geometric specifications,and loading conditions. new model-calculated capacitance values are found to be in excellent agreement with published experimental results with a maximum deviation of 1.7,and a maximum deviation of 1.5 has been observed when compared with fea results. the model can help in improving the accuracy of the design methodology of cmut devices and other mems-based capacitive type sensors built with square diaphragms. copyright © 2011 md mosaddequr rahman and sazzadur chowdhury.