Coefficients of Coupled-Mode Equations for Reversal of Directivity Transducers on a 50°Y-25°X La₃Ga₅SiO₁₄ Substrate

Computed results of all the coefficients of coupled-mode equations are presented for a transduction center-shift-reversal-of-directivity transducer (TCS-RDT) and an electrode-width-controlled-reversal-of-directivity transducer (EWC-RDT) on a 50°Y-25°X La₃Ga₅-SiO₁₄ substrate. To the best of our knowledge, an EWC-RDT is being reported for the first time. The aluminum electrode thickness and width dependences of the coefficients are investigated in detail. Numerical results show that we can choose pairs of width and height of the electrodes for a distance of λ/8 with λ being the surface acoustic wave (SAW) wavelength at the center frequency between the reflection center and the transduction one. Our results of the insertion loss for a filter composed of a TCS-RDT and two split-electrode interdigital transducers (IDTs) agree well with those of the earlier experiments.