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Behavioral modelling and simulation of a MUT-based pulso-echo system

Author(s): S. Mir, L. Rufer, C. Domingues

Doc. Source: 2nd International Workshop on Microfabricated Ultrasonic Transducers

Pages: 18-24

This paper describes the design, modeling and simulation of a micromachined ultrasound transducer (MUT) in a pulse-echo application. The microsystem, used as emitter and receiver of ultrasonic signal, consists of a bulk micromachined suspended membrane. The membrane is thermally actuated at its resonance frequency (. 40 kHz) during emission. During reception, a piezoresistive bridge placed on the membrane is used for monitoring the membrane deflections. The resonance frequency of the membrane is tuned to the emitted frequency by keeping the membrane at the same temperature, achieving then maximum sensitivity. This paper presents in detail the behavioral modeling and simulation of the whole system using the microsystem in the emitter and in the receiver mode. Some MEMS parts and the acoustic waves propagation are modeled using an Analogue Hardware Description Language (Verilog-A). The associated electronics are implemented in CMOS and the overall system is simulated with the SpectreHDL simulator in the CADENCE environment. We consider a 0.8 µm CMOS process combined with the back-side bulk micromachining of the silicon wafer with SiO2 etch-stop. This design that is fully CMOS compatible has the advantage in its simplicity with respect to the capacitive transducer. The employment of only one element in the dynamic structure simplifies the design considerations in terms of mechanical stability and membrane damping as well as the fabrication process.