Analysis of bias effects for a capacitive-micro-ultrasonic-transducer

DC bias voltages are commonly employed in using capacitive micro-ultrasonic transducers (CMUT) for their signal/noise ratio and sensitivity improvements. On the other hand, deformations of CMUT membranes are usually limited by the applied biasing voltages. Bias effects for CMUTs are investigated and modeled in this research, whether the transducers are operating in their transmitting or receiving modes. As to model a multi-energetically coupled CMUT device, the DC bias voltage effects are first examined based upon conversion from electrical energetic domain into mechanical energetic domain. The bias is represented as mechanical impedance, which is integrated with a modified CMUT mechanical equivalent circuit model, and subsequently interfaced with an acoustic equivalent model. This innovative model is implemented to derive physical relations and transfer functions for CMUT transducers, when they work in transmitting or receiving modes through gas or fluid media.