Parameters of coupling-of-modes equations for a natural single-phase-unidirectional transducer on a La3Ga5.5Nb0.5O14 substrate

Parameters included in coupling-of-modes equations such as coupling coefficients, transduction coefficients and electrostatic capacitances are theoretically determined for a natural single phase unidirectional transducer (NSPUDT) on a La3Ga5.5Nb0.5O14 substrate with Euler angles of (110 degrees, 145 degrees, 145 degrees) and an electromechanical coupling coefficient larger than quartz. In the hybrid finite-element method (HFEM), used for determining these parameters, all the effects of anisotropy of the substrate, piezoelectric perturbation, mechanical perturbation and energy storage are taken into account. The electrode thickness and width dependence of the parameters and the excitation characteristics of NSPUDT are investigated in detail. The parameters obtained by the present method are compared with those obtained by the perturbation method. Furthermore, numerical results for the frequency characteristics of NSPUDT are compared to the experimental data, and the validity and usefulness of the present method are demonstrated.