Crosstalk effects caused by the geometry of piezoelectric elements in matrix ultrasonic transducers

Abstract

Crosstalk is a result of the deficiency in the electrical or mechanical isolation between elements. It is a function of the proximity between piezoelectric elements of the transducer or between connections. It can be caused by a series of factors, such as: the deficiency in the electromagnetic shield, the capacitive effect between the elements or the electrical connections, or by the transmission of vibration modes to adjacent elements due to insufficient mechanical isolation. It also depends on the geometry of the elements and the connecting material between elements. The evaluation of the crosstalk effects caused by the geometry of the piezoelectric elements in matrix ultrasonic transducers is presented. Measurement methods of the radiation patterns and vectorial impedance for the identification of crosstalk are described. The procedure of the measurement of crosstalk, done by Sanchez Dominguez and von Kruger (2002), was applied to an eight elements phase onedimension matrix transducer for Doppler ultrasound application. In fact, two cases are presented, in one of them a piezoelectric element of the matrix with initial dimensions of 10.0 × 4.4 × 0.66 mm was used, and in the other case a piezoelectric element with initial dimensions of 10.0 × 0.7 × 0.66 mm was used (element are made of Lead Zirconate Titanate, also called PZT). From the results we deduce that it is possible to reduce the crosstalk effect using insulating material with low electromechanical coupling coefficient between the ceramics of the array or using materials that promote good mechanical insulation between the ceramics.