VHDL-AMS behavioural modelling of a CMUT element

Abstract

This paper reports the development, implementation and simulation of a behavioural model written in VHDL-AMS for a capacitive micromachined ultrasonic transducer (CMUT). Unlike previous behavioural models, this model incorporates the non-linear electro-mechanical relation of the CMUT. VHDL-AMS was chosen for the ease with which it can be used to implement these relations, and for its portability between software platforms. To the best of the authors' knowledge, this is the first reported VHDL-AMS model of a CMUT. The simulation results demonstrate that the model can be used to sumulate a number of scenarios, including frequency responses, time responses and effects of DC bias voltage. Results are compared to a finite element method model, and show excellent agreement in resonant frequency and a 16% error in pull-in voltage.