P2P-10 Electrostatic-Mechanical Direct Coupling and FEM-BEM Coupling for CMUT Electroacoustic Parameters Identification

Capacitive micromachined ultrasonic transducer (CMUT) arrays are seen as a promising way to improve ultrasound-imaging definition and they may supplant piezocomposite arrays for such applications. However, as a new technology it needs to be evaluated and modelling can help to design devices using cMUT technology. Implicit finite element codes are commonly used to model cMUT devices, but to take into account the fluid surrounding the device $radiation, scattering and the inter-mutual acoustic influence of the CMUT arrays cells - the boundary element method (BEM) coupled with the finite element method (FEM) can be advantageously used. Moreover the standard electromechanical coupling is either weak or lumped and cannot be used to model CMUT accurately. A FEM-BEM coupling together with an electro-mechanical direct coupling as add-on modules for ANSYSreg were developed. This paper will show how to identify exact nonlinear equivalent circuit lumped parameters from a FEM and FEM-BEM simulation. The electrical and motional branch of the circuit is identified by resonance and antiresonance modal analysis. The radiating impedance is computed using a FEM-BEM coupling in frequency domain. Finally the transducer insertion loss is evaluate