An Experimental Investigation of the Cross-Coupling between Elements of an Acoustic Imaging Array Transducer

Abstract

In a phased array acoustic imaging transducer, the cross coupling between elements of the array can lead to a loss in range resolution, cause an increase in rolloff with angle of the sector scan, and increase the ringdown time.

In this paper, we present results of an experimental investigation of an acoustic mode that couples the elements through the propagation of surface waves on the surface of the acoustic absorber. These results indicate that the strength of the mode is enhanced by the coherent reflections from adjacent neighbor elements which act as efficient reflectors of the surface waves. We also demonstrate a technique whereby reflections can be made to interact destructively to reduce the strength of that coupling mode. A further reduction can be obtained by stiffening the structure by bonding to the tops of the elements a thick brass foil and by using it as a common ground connection.