The effect of mass-loading on velocity dispersion and coupling of STW

Blotekjaer´s theory, extended by Hashimoto and coworkers, for analyzing surface transverse waves has been modified in the part concerning the effect of finite electrode thickness. First order Datta-Hunsinger´s surface boundary conditions have been introduced in the effective permittivity of the substrate, to account for the mechanical loading. The dispersion STW velocity curves have been obtained over the entire frequency stopband, including the interval where intensive excitation of bulk modes occurs. The effective permittivity also allows obtaining the electromechanical coupling of the grating mode. Its numerical analysis reveals a strong dependence on the metalization ratio and mass-loading, in close agreement with results from Hasimoto´s discrete Green function theory