Structure Design And Simulation Of Capacitive Micromachined Ultrasonic Transducers(cMUT)

Piezoelectric ultrasonic transducer is sound-electronic converor, which is commonly used in the field of ultrasonic. But the large impedance mismatch of air and ordinary piezoelectric material implies that traditional piezoelectric ultrasonic transducer is inherently an inefficient ultrasonic source. Certainly, in order to improve efficiency, a matching layer is usually placed in between the piezoelectric and air. But the bandwidth is reduced at the same time. As the development of MEMS technology , a new kind of ultrasonic transducer, capacitive micromachined ultrasonic transducers, is designed. cMUT is made using surface micromachining techniques, so the shortcomings of traditional PZT are overcame. What's more, cMUT is an alternative to the PZT because of being easy prone of manufacture, small dimension, low noise, wide operating temperature range and being easy to integrate with electronics.Based on the description above, the study on cMUT is presented. According to the oversea research information, a practical cMUT structure and its flow of manufacture techniques are designed, then simulated and imitated. Finally, the test system of cMUT's performance is presented.The following are main achievements of this thesis:1. Study the national and foreign reference and conclude the latest development cMUT. Main concern is basic structure, the operation principle , the excitation methods, the influence on performance by structure parameters, the manufacture techniques and the methods of modeling and simulation.2. Present a kind of cMUT structure, which can be used on test, and its corresponding method of manufacture based on the surface micromachining techniques.3. Create the 3-D model of the structure and simulate with static and modal analysis using finite element analysis software ANSYS. The resonant frequency and the vibration graphs are obtained.4. Using coupling domain of ANSYS and parameter design language (APDL), the structure is simulated by the way of force-electric coupling modal and harmic analysis. Then the structure is confirmed according to the analysis results.5. Present the designing of the system for testing cMUT's performance.