Modeling, design and characterization of limited diffraction ultrasonic transducers

Ultrasound piezoelectric transducers are used in medical applications and for non-destructive testing of materials. Among them, a special type, the so named limited diffraction ultrasonic transducers present a great depth of acoustic field, without important effects of diffraction, besides other qualities, which make them optimal in applications of medical images. In this paper, the design of a class of these transducers is explained through a simple technology that uses a method of direct polarization. The application of the Finite Elements Method to simulations in the design process of not uniformly poled transducers, as well as the experimental characterization of their dynamic behaviour, is described. The comparison of the experimental results with those simulated, using Finite Element Analysis, guarantees with an excellent agreement the use of this powerful method of simulation, during the construction and characterization of limited diffraction transducers.