The impact of element taper and inhomogeneous material properties on ultrasonic array performance

The computer simulation of an ultrasonic transducer is typically an idealized representation of the device and assumes perfectly parallel faces and spatially invariant material properties. In the real world however, these assumptions are not necessarily valid. Fabrication processes such as dicing may result in a quantifiable taper across the height and/or length of a transducer array element. Furthermore, material properties, in particular those for piezoelectric materials, may vary appreciably across the length of an array element. Both of these "parasitic" facts-of-life will impact a device's performance to some extent or another, and in some cases may serve to degrade device performance below acceptable limits. The purpose of this paper is to study and quantify the impact that non-idealized geometries and inhomogeneous material properties have on an ultrasonic transducer's resonant response.