The propagation of SAW in guiding structures by using the angular wave spectrum

The design of narrowbanded SAW filters for modern communication satellites involves calculation of SAW propagation in interdigital transducers with long lengths in comparison with the transducers´ aperture and hence the acoustic wavelength. Owing to mass loading and short circuited surface, the slowness curves inside and outside the transducers will be different and the transducers will behave as guiding structures. In most cases we are only interested in the field across the aperture of the fingers. Here we will utilize this fact and present a fast and accurate method for calculating the propagation-inside a guiding structure. The theoretical analysis shows that a SAW propagation description is obtained by modifying the angular wave spectrum. A new busbar structure suited for narrowbanded SAW filters are used for both the theoretical analysis and the measurements