Theoretical Determination of Equivalent Circuit Parameters for Natural Single-Phase Unidirectional Surface Acoustic Wave Transducers.

This paper proposes a method for theoretical determination of the circuit parameters in the equivalent circuit for the natural single-phase unidirectional transducer (NSPUDT), which is one type of unidirectional surface acoustic wave interdigital transducers. The finite element method was used to find the upper and lower edge frequencies of the shorted and open-ended gratings corresponding to the shorted and open electrical terminal of the NSPUDT, the potential standing wave distribution and the static capacitance per pair of NSPUDT, needed for determination of the circuit parameters. Due to the analysis method, the anisotropy of the substrate, the electrical perturbation effect, the acoustic perturbation effect, and the energy storage effect can be taken into account. Actually, the equivalent circuit parameters of the NSPUDT on an ST-cut 25° X-propagation quartz substrate were computed and the reflection and excitation characteristics of the surface wave were derived. From a comparison with the experimental values, the validity and usefulness of the present method is confirmed. [ABSTRACT FROM AUTHOR]