Electroacoustic modeling and characterization of an ultrasonic projector

Abstract

Ultrasonic projectors are new type ultrasonic transducers that take advantage of the ultrasonic wave emitted on the rear face of the transducer. It consist in an acoustic symmetrical design where both waves generated on the faces of the piezoelectric ceramic are collected in phase with a 45° angle wedge resulting in an increase of the sensitivity. In this case, the absence of backing endows that the conventional design rules of a transducer cannot be directly applied. In this work, the electroacoustic modeling and characterization of such projector is reported. Using the KLM well known model, the electroacoustic response of a projector in based on a piezoelectric ceramic with one matching layer is calculated. Simulations show that the optimal acoustic impedance of the matching layer should be lower than for conventional transducers leading to a bandwidth of approximately 50%. The characterizations of such transducer based on PZ27 (Meggit/Ferroperm) and a lead free material PIC700 (PI Ceramic) have been carried out. Bandwidth and sensitivity are reported. They are found close to the simulation results and demonstrate that these new types of transducers has to be designed according new trends compared to conventional transducers.