Design of ultrasonic transducers with controlled radiation patterns

This paper presents the design considerations for an ultrasonic transducer that consists of a cylindrical metal housing and a piezoceramic disc attached to the underside of the housing. The effects of housing geometry on the radiation directivity are studied by changing the curvature of the front surface of the metal housing. The near field behavior of the ultrasonic transducer is studied using the impulse response approach while the far field behavior is analyzed using Fraunhofer´s approximation. The expressions for the near field and far field regions are shown to contain the housing curvature and the amplitude distribution on the surface of the housing. Furthermore, the vibrational modes of the transducer structure are determined using the finite element method. The results obtained show that the geometry of the transducer housing has significant effects on the radiation characteristics of the transducer