Study of Surface Acoustic Waves under Periodic Grating Structures

-The propagation characteristics of the surface acoustic waves (SAW) propagating under the periodic metal grating on ST-cut quartz substrates were theoretically investigated in order to achieve more accurate design of the devices. The theoretical method used here is based on Floquet’s theorem using the space harmonics method (SHM) as an orthogonal function set. The boundary conditions are satisfied by solving the real boundary integral equations, which are derived from the method of weighted residuals for a period of each region, i.e., substrate, metal, and free space. The boundary integral equations are solved by using the Galerkin procedure. The periodic strip gratings are investigated, considering the convergence of the numerical computation for the number of the space harmonics. The dispersion properties for shorted and open gratings are derived from SHM. Finally, we can calculate the parameters of coupling of modes (COM) and design a resonator to prove the accuracy of propagation analysis. Key-Words: Surface acoustic wave, Periodic grating, Space harmonic method, Coupling-of-Modes theory, Dispersion curves, Self-coupling coefficient, Reflection coefficient.