Analysis of SAW grating waveguides considering velocity dispersion caused by reflectivity

Conventional SAW grating waveguide analyses based on the scalar potential theory regard the phase velocity in the grating region as a constant. The velocity at the center frequency of the stop band was often used as a constant in those analyses. In reality, velocity dispersion is caused by the reflectivity of finger electrodes, and the velocity changes near the stop band. In this paper, a new approximate analytical model of SAW grating waveguides is proposed. This model includes the effect of the velocity dispersion, by placing a longitudinal component of wave number in such a way that it becomes a solution of the coupling-of-modes equations. To verify the adequacy of the model, 2-port resonators on 36.5°Y-X quartz and 45°X-Z Li₂B₄O₇ are measured and compared with the computational results.