The use of fractal geometry in the design of piezoelectric ultrasonic transducers

Mulholland, Anthony and MacKersie, John and O'Leary, Richard and Gachagan, Anthony and Walker, A. and Ramadas, Sivaram Nishal; (2011) The use of fractal geometry in the design of piezoelectric ultrasonic transducers. In: 2011 IEEE International Ultrasonics Symposium (IUS). IEEE, USA, pp. 1559-1562. ISBN 9781457712531 (

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The geometry of composite piezoelectric ultrasonic transducers is typically regular and periodic with one dominant length scale. In many applications there is motivation to design transducers that operate over a wide bandwidth so that, for example, signals containing a broad frequency content can be received. The device's length scale will dictate the central operating frequency of the device and so, in order to construct a wide bandwidth device, it would seem natural to design a device that contains a range of length scales. The objective of this article therefore is to consider one such transducer design and build a theoretical model to assess its performance. For the composite geometry a fractal medium is chosen as this contains a wide range of length scales. Numerical results of a theoretical model are presented. They suggest that this device would have a three-fold improvement in the reception sensitivity bandwidth as compared to a conventional composite design. Finite-element analysis provides information on the effect of poling on the device's performance. A preliminary experimental investigation was undertaken, with a Sierpinski gasket fractal transducer design, and good correlation between the simulated and experimentally measured operation was observed.