Frequency Steerable Transducers for Ultrasonic Structural Health Monitoring

Ultrasonic Structural Health monitoring systems are typically implemented through phased arrays featuring a large number of piezoelectric transducers. However, the permanent installation of such a large number of transducers could hamper the widespread field deployment of SHM systems. To this aim, a possible solution is in the shaping of the piezoelectric transducer electrodes to achieve the capability of steering the ultrasonic beam by simply controlling the central frequency of the actuated pulse. This solution enables the imaging of large 2D areas by actuating just two differential signals. In this work, some recent realizations of Frequency steerable transducers (FSATs) will be presented, detailing the design, simulation, and experimental characterization strategy and the signal processing techniques which can be applied on the acquired signals. It will be shown that FSATs offer several features, such as inherent hardware directivity, and reduced sidelobes, which are essential in the realization of the next generation of ultrasonic Structural Health Monitoring systems.