SAW reflections on ST-cut quartz grazing angles

Characteristics of surface acoustic wave (SAW) propagation across straight boundaries between areas of different surface conditions must be known to predict wave propagation in SAW waveguides. Actual waveguides consist of combinations of free and metallized surface, and also areas with metal strips such as in interdigital transducers. In particular, waves will impinge on the discontinuities at low grazing angles in wide waveguide structures, as is often the case in SAW filters. Laser probe measurements on reflection at boundaries between several of these surface types on ST-cut quartz are reported. The measurements have given a new value of the anisotropy parameter b =1+γ≈1.29 for ST-cut quartz. Using this parameter value the measured results seem to be in general agreement with published theories