A thin film technique for spatial apodization of disc-shaped piezoceramic transducers

Abstract

Conventional piezoelectric disc transducers suffer from some inherent disadvantages as a result of diffraction and multimode wave interaction within the radiated sound field. It is shown that significant improvements may be achieved by employing a continually varying resistive taper as a front or rear face electrode, thereby minimizing the influence of aperture diffraction, radial mode coupling, and electric field variations on the spatial response. The theoretical operation of such devices is discussed and good agreement is obtained from a selection of experimental observations on different transducer materials.

A New Ultrasonic Transducer Combining Three Modes: High Axial Resolution, High Transverse Resolution and Standard Modes

“…Hayward et at. [5] employed a continuously varying resistive thin film taper as front or rear electrode. Different arrangements ofaxisymetric electrodes partly covering the surface of the piezoelectric element have been described [6,7].…”

A model to predict the transient radiation from segmented annular apertures radiating into solid media

“…To further develop the theory, vector particle velocities and displacements are required [6]. However, the current application is such that (8) can be used to predict the compressional component with a reasonable degree of accuracy [lo].…”

The modelling and design of controllable composite transducers

“…Data interpretation with respect to propagation medium characteristics and any associated inverse signal processing is thus limited to restricted regions within the transducer sound field. This problem has attracted considerable attention and several techniques for controlling the spatial field of disc transducers have been reported in the literature [1,2,3]. One method which the authors have found successful [3] is illustrated in Figure 1, where a continuously varying resistive taper and appropriate choice of electrode pattem permit suppression of plane or edge components associated with circular aperture diffraction.…”

“…This problem has attracted considerable attention and several techniques for controlling the spatial field of disc transducers have been reported in the literature [1,2,3]. One method which the authors have found successful [3] is illustrated in Figure 1, where a continuously varying resistive taper and appropriate choice of electrode pattem permit suppression of plane or edge components associated with circular aperture diffraction. As shown in Figure 1, with 'edge wave' suppression, the resistive taper is utilised in order that the applied electric field decreases from a maximum at the centre to zero at the edge in a controlled fashion.…”

“…As shown in Figure 1, with 'edge wave' suppression, the resistive taper is utilised in order that the applied electric field decreases from a maximum at the centre to zero at the edge in a controlled fashion. A particular feature of such a shaded transmitter is that the radial modes 1051-0117/90/0000-0393 $1.00 0 1990 IEEE associated with some ceramic devices are suppressed [3]. Altematively, the resistive taper is employed such that with 'plane wave' suppression the electric field is maximum at the disc edge and is r e d u d to zero in the centre, again in a controlled manner.…”