An improved lumped element nonlinear circuit model for a circular CMUT cell.

Area of Science:

• Microelectromechanical Systems (MEMS)
• Ultrasonic Transducers
• Circuit Modeling

Background:

• Existing large signal equivalent circuit models for circular capacitive micromachined ultrasonic transducer (CMUT) cells have limitations.
• Accurate modeling is crucial for predicting CMUT performance, especially near collapse conditions.

Purpose of the Study:

• To present a corrected and extended large signal equivalent circuit model for circular CMUT cells.
• To ensure energy and power preservation within the equivalent circuit model.
• To accurately predict CMUT behavior up to membrane-substrate contact.

Main Methods:

• Rederiving the force model to preserve energy and power in the equivalent circuit.
• Developing a model capable of predicting the entire CMUT behavior until membrane contact.
• Deriving the small signal equivalent circuit from the large signal model for any bias condition.

Main Results:

• The enhanced model accurately predicts CMUT behavior, including collapse condition and voltage.
• It describes the voltage-displacement interrelation and force equilibrium before and after collapse.
• Model predictions show excellent agreement with finite element method (FEM) simulations.

Conclusions:

• The corrected and extended large signal model provides a comprehensive tool for CMUT analysis.
• The model facilitates the prediction of critical CMUT parameters and behavior.
• It is readily implementable in circuit simulation tools for design and analysis.