RECEIVING MODE ENHANCEMENT OF CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCERS BY MEMBRANE STRUCTURE MODIFICATIONS
Xiao Jiang1,2, Yuan Yu Yu1,2, Jiu Jiang Wang1,2, Xin Liu1,2, U Kin Che2, Sio Hang Pun2, Mang I Vai1,2, Peng Un Mak1
1University of Macau, China;
2State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, China
Similar to traditional piezoelectric transducer, Capacitive Micromachined Ultrasonic Transducer (CMUT) is a kind of MEMS-based ultrasonic transducer which can act either as a transmitter or a receiver. In comparison, it owns several advantages over the traditional piezoelectric transducer. As to the reception performance, it is important to the overall performance and very few published papers researched on the behavior of receiving mode of CMUTs.
This paper presents FEA models (via COMSOL Multiphysics) of receiving CMUTs working as conventional mode in water with two modified membrane structures: namely slotted membrane and corrugated membrane. By modifying the membrane structures, effective membrane thickness will decrease. This will decrease overall system stiffness and hence increase the membrane deflection. With the modified membrane structures, both static membrane deflections biased by DC voltage and dynamic membrane displacement caused by external acoustic pressure will increase. These will lead to the enhancement of reception performance.
Initial FEA simulations show that by using the modified membrane structures in given configurations, the collapsed voltage and center frequency will reduce. Moreover, both the electromechanical coupling coefficient and receiving sensitivity are improved up to 20.9% & 50.5% for slotted membrane and 5.0% & 38.3% for corrugated membrane, respectively.