Ultrasonic Transducers Based on Mems Technology

Abstract

Sound frequencies above than human hearing range (20Hz-20 kHz) are referred to as newlineultrasound. The properties of ultrasound remains same as audible sound waves, only that newlinethey can t be heard by human beings. Ultrasonic transducers are newlineemployed in many fields to generate and receive ultrasound. Based on different working newlineprinciples, ultrasonic transducers are of many types namely, magnetostrictive transducers, newlineelectrostatic transducers, piezoelectric transducers and electromagnetic transducers. With the development in micromachining techniques in device fabrication, with the advantage of having integration with the on chip electronics, micromachined electrostatic transducers have been developed as a substitute for the piezoelectric transducers. Based on the capacitive principle with micron size range, the Capacitive Micromachined Ultrasonic Transducer (CMUT) offers many advantages and overcomes disadvantages of the existing piezoelectric transducers. Due to micromachining fabrication methods, the CMUT provides wider fractional bandwidth, low impedance mismatch, low cost due to batch fabrication and possibility of integration with associate electronic circuits. CMUTs have many airborne ultrasound and underwater imaging applications. Airborne applications include ultrasonic gas flow meters, range finding, anemometry applications, and detecting flaws and cracks. For underwater imaging applications, optical systems finds many drawbacks like low visibility range, low resolution, longer imaging times etc. CMUTs on the other hand has the capability to enter in the muddy water, offering higher resolutions, fast imaging over wider ranges. These days CMUTs are used for underwater commercial applications like construction, fishing, archaeology and for surveillance purposes. In this work, parallel plate model of CMUT is developed in COMSOL, with the description of its electrical equivalent model, small signal analysis is carried out along with mathematical modelling for important parameters. newline