Extraction of the SAW attenuation parameter in periodic reflecting gratings

In this paper, the extraction of the coupling-of-modes (COM) model attenuation parameter gamma in a finite grating is considered. We use test structures comprising identical transmitting and receiving transducers and a grating centered in the acoustic channel along the propagation direction of the surface acoustic wave (SAW). The extraction procedure proposed is based on studying the magnitude of the ratio of the reflection and transmission coefficients of the grating, R/T, obtained through time gating from the S parameter measurements of the test devices. In particular, we found that the level of the notches of R/T directly depends on the attenuation of SAW in the grating. A simple closed-form expression for the attenuation normalized to the grating length, gamma lambda0, depending on the characteristics of absolute value R/T, is given. The proposed method is applied to the measurement data for selected grating topologies to yield estimates of the attenuation.