Diffraction in slanted finger SAW filters

The purpose of this paper is to describe diffraction effects on slanted finger interdigital transducers (SFITs). In order to analyze the diffraction effects, two methods to calculate SAW amplitude profiles radiated from an SFIT are presented. One is to calculate the electric power of the acoustic ports in the Smith's equivalent circuit for the sub-filters with different center frequencies, which were obtained by dividing SFITs into some channels. The other is to calculate the SAW intensity at an observation point using an angular spectrum method. The frequency responses of the SFIT filter with a center frequency of 40 MHz and a bandwidth of 6 MHz are calculated using the angular spectrum method. Good agreements between theoretical and experimental results are obtained.