Three-dimensional beam directivity of phase-steered ultrasound

A model is developed to compute the three-dimensional far-field acoustic pressure distribution of the waves radiated from an ultrasonic linear phased array with finite elemental dimensions. Based on the model, the three-dimensional beam directivity function is introduced and analyzed to investigate the effects of geometric parameters on the steering performance. It is confirmed that the elevation dimension does not influence the beam directivity in the azimuthal plane. This is not true, however, in nonazimuthal planes. In general, increasing the elevation dimension reduces the energy leaking into nonazimuthal directions. The influences of other transducer parameters, including the number of elements, interelement spacing, and aperture length, are also investigated. It is found that they have only trivial effects on the sideleaking, although they are the important factors that influence the directivity in the azimuthal plane.