VHDL-AMS Modeling Approach To Electrostatically Actuated Mems Devices

MEMS is defined as an integration of sensors, a signal processing part and actuators in a single chip for improved accuracy, reliability and functionality. Computer-aided-design is an indispensable tool to reduce time-to-market and cost. It is essentially based on the availability of accurate and efficient macromodels which can capture the complex non-linear coupling between multiple physical fields such as electrical, mechanical and thermal domains, yet be fast to insert into a system dynamics simulator. Our work is focused on the design of electrostatically actuated MEMS devices, with emphasis on electrostatic and mechanical effects, not only because they have found wide applications in many fields but also there is a tight integration with electronics. We develop a lumped model of an electrostatic combdrive microresonator which is represented in a set of ordinary differential and algebraic equations (DAEs); The continues systems characterized by partial differential equations can be modeled by modal superposition methods. In order to illustrate this method, the electrostatically actuated fixed-fixed beam is examined and the macro-model which is represented by a small set of ODEs is developed from a few finite element simulations. Because of the relatively small number of equations, the model can be simulated in reduced time. By using hardware description language such as VHDL-AMS, these models can be easily inserted into circuits or system simulators for the whole system design and optimization.