Features of the acoustic field of angle surface-wave transducers

The influence of process features in the fabrication of angle transducers (deviation from uniform distribution of mechanical stresses/strains over their transmitting/receiving surface) on the acoustic field of excited surface waves has been investigated. Calculation was carried out within the parabolic approximation by replacing a real angle transducer of surface waves with a linear source located on the surface of a waveguide (control object) with a nonuniform (cosine) distribution of stress amplitudes. The expressions for the stress (strains) at an arbitrary observation point for a point receiver (reflector) and for the stress averaged over the receiver plane are obtained in complex form. The coordinate dependences of the stress amplitudes and phases have been calculated for typical technological modes; the calculation results are presented as plots. It is shown that the effect of deviations from uniform distribution is strongest in the transition (from the near-to far-field) zone, where nonuniformity of displacements of 10–15% at the edges of a piezoelectric cell causes a change in their amplitude by 15–30% in comparison with uniform distribution; this must be taken into account when estimating diffraction corrections. The possibilities of experimentally verifying the degree of nonuniformity of the stress distribution over the angle-transducer surface are discussed.