A computationally efficient nonlinear system model for CMUT arrays

We present a fast lumped model that predicts the electrical input-output behavior of an ultrasound system using CMUT arrays with arbitrary membrane/electrode geometries. Model capabilities include selection of arbitrary drive signals and transmit-receive circuit impedances for individual array elements, enabling accurate modeling of arrays of single and multiple electrode CMUTs for different ultrasound modalities in a computationally efficient manner. Given the CMUT system description, the pressure at an arbitrary point in the immersion medium and individual membrane displacements are calculated in the time domain for transmit mode. In receive mode, the output electrical signals are calculated as if another ultrasound source is present in the immersion medium. Pulse-echo operation is considered as the transmit-receive mode where the incident field is generated by the image of the CMUT array itself. An example CMUT system consisting of a single circular membrane with multiple electrodes is used to validate all these different modes through comparisons with COMSOL. The results show the ability to capture the nonlinear CMUT behavior accurately and the versatility of the model for different scenarios.