Theory for shear horizontal surface acoustic waves in finite synchronous resonators
An analytic approach is developed for simulating synchronous resonators employing shear horizontally polarized surface acoustic waves, such as surface transverse waves, and leaky surface acoustic waves on LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The approach, based on a simplified parametrized Green's function theory, allows the description of the localization of the wave and the interaction with bulk acoustic waves. An analytic expression is found for the harmonic admittance of an infinite periodic electrode array, and approximate corrections for finite structures are presented. The model enables fast computation of the admittance of synchronous resonators, and it compares favorably with experiments and numerical simulations.
Propagation of Transverse Surface Acoustic Waves in Rotated Y-Cut Quartz Substrates Under Heavy Periodic Metal Electrodes
Abstmct-A theory of the propagation of transverse surface acoustic waves on a piezoelectric substrate with heavy periodic metal electrodes on the surface is presented. The mechanical properties of these electrodes are assumed to be nonnegligible. Dispersion relations for waves near the stopband of the periodic electrode array are analyzed. It is found that the mass of the electrodes exerts a considerable effect on the shape and mutual positions of the stopbands for short-circuited and electrically isolated electrodes. The discussion is based on an approximation for the effective surface impedance that relates the amplitudes of the electric and elastic fields observed at the surface of a piezoelectric substrate. The parameters of this approximation are given for rotated Y-cut quartz substrate. The theory presented can readily be generalized to the case of Rayleigh surface waves.
Dispersion of Surface Elastic Waves Produced by a Conducting Grating on a Piezoelectric Crystal
The dispersion relation for surface elastic waves propagating under a thin metallic grating on the basal plane of a hexagonal piezoelectric crystal is investigated theoretically. Purely reactive loads are assumed connected between adjacent electrodes of the grating. The effect of mass loading due to the grating is neglected. The presence of the grating imposes periodic boundary conditions on the piezoelectric fields associated with the surface wave. The resulting boundary‐condition problem is solved to obtain the dispersion relation for surface elastic waves. For a material with a large electromechanical coupling coefficient an inductance connected between adjacent electrodes can cause a large reduction in the phase velocity of the surface wave. (For example, in PZT‐4, this reduction is about 10%.)