Electrostatically Variable SAW (Surface Acoustic Wave) Delay Lines - Theory and Experiment

摘要

A theoretical and experimental investigation has been made of surface acoustic wave (SAW) time-delay change produced by the application of a dc electric field. Measurements were made on the three high-coupling cuts of lithium niobate for the electric field applied in the planer of surface with a novel electrode configuration and normal-to-the-surface with a standard 'convolver' plate. A theory has been developed for the normal field configuration, where the electric field is uniform, and for the in-plane case, where the field is nonuniform. The dominant contribution for the latter comes from the center of electrodes. For the 38 X-cut of lithium niobate, the normal field sensitivity (fractional time-delay change per applied electric field gamma) is 141 x 10 to the -12th power m/V, while gamma for the in-plane field is 6 X 10 to the -12th power m/V. The in-plane configuration has the advantage of having lower insertion loss and dispersion as the SAW does not have to propagate through a metal electrode.