Analysis of an electrode-width-difference-reversal-of-directivity transducer on a La21Ga5.5Nb0.5O14 substrate

The parameters included in coupling-of-modes equations such as coupling coe fficients. transduction coefficients and electrostatic capacitances are the oretically determined for an electrode-width-difference-reversal-of-directi vity transducer (EWD-RDT) on a La3Ga5.5Nb0.5O14 substrate with Euler angles of (108 degrees, 148 degrees, 144 degrees). In the hybrid finite-element m ethod (HFEM). used for determining these parameters, all the effects of ani sotropy of the substrate, piezoelectric perturbation, mechanical perturbati on and energy storage are taken into account. Numerical results for the fre quency characteristics of insertion loss and for the directivity are compar ed to the experimental data, and the validity and usefulness of the present method are demonstrated. Furthermore, the electrode height dependence of t he parameters and the directivity of EWD-RDT are investigated in detail.