Experimental study of propagation loss in SAW grating waveguides

This paper discusses the energy loss in surface acoustic wave filters using grating waveguides. Waveguides formed with aluminum grids, which have the period detuned from the Bragg condition, are used to evaluate the propagation loss without the effects of the reflection. The propagation loss in the waveguide on ST-cut quartz is evaluated as small as 2×10^-3 dB/wavelength. It is revealed that the extra energy loss arises at the short waveguide length and before SAWs launched by the IDT enter the waveguide. It is shown that increasing the aluminum film thickness or the waveguide width reduces the extra energy loss. Based on the experimental study, it is confirmed that the insertion loss in the reflector-filter using a SAW grating waveguide is reduced by 2 dB