A complex impedance model for SAW and LSAW propagation in periodic grating

In this paper, we propose a Complex Impedance Model (CIM) for SAW and Leaky SAW (LSAW) propagating under periodic gratings. CIM starts with the postulation of impedance discontinuity, based on which a reflective grating is equivalent to a transmission line with complex impedance and complex propagation phase shift. As a result, the reflection and transmission of SAW and LSAW can be expressed in simple, analytical formulae. The model is compared with COM analysis and entire equivalence proved. Also a method is developed to extract CIM parameters such as center frequency, impedance mismatch coefficient, propagation attenuation coefficient and shunt susceptance element. As an example, numerical results for LSAW under gratings on 36-YX-LiTaO/sub 3/ substrate are presented.