Nonlinear model with lumped parameters for asymmetric CMUTs

An equivalent circuit model is developed for a special kind of CMUTs called asymmetric CMUTs, containing a membrane and two split bottom electrodes. The macromodel contains subcircuits representing different vibration modes from modal participation theory. By using a lumped parameter model, the system is not restricted around an equilibrium point, and remains valid under any kind of excitation voltage. The model predicts the frequency response of the CMUT for different media and accounts for the spring softening effect. We compare our results against FEM simulations and experimental measurements.