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A theory of interdigital transducer is presented that accounts for the surface acoustic wave diffraction. It is formulated with help of the Blotekjaer, Ingebrigtsen, and Skeie expansion method used earlier in the plane-wave theory. Now, the electric field is applied to the breaks in the strips making parts of them polarized with different potentials. This way the finite aperture width transducers are modeled residing within an infinite system of periodic strips. Closed expressions are derived for system working below the Bragg condition. The theory is open for further development accounting for elastic strips, pseudo surface, leaky or even surface skimming bulk waves, for any frequency range, including Bragg reflection exploited in surface wave resonators.

A resonant phenomenon is investigated for the generation of interfacial waves when bulk waves are scattered by in-plane periodic cracks embedded in an isotropic elastic body. A new method of analysis is developed and numerical results are presented. This analysis can have useful applications involving the generation of surface acoustic waves by comb transducers.

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A system of periodic elastic strips (each one considered as a piece of a plate) is characterized by a matrix relation between the Bloch series of displacement and traction at the bottom side of the system. Both these mechanical fields are involved in the boundary conditions at the contact plane between the strips and the substrate supporting a Rayleigh wave. The analysis exploits the mechanical field expansion over the plate modes, including complex modes; numerical results satisfy the energy conservation law satisfactorily. The derived planar harmonic Green’s function provides an alternative tool for investigation of surface waves propagation under periodic elastic strips, with respect to pure numerical methods mostly applied in the surface acoustic wave devices literature. Perfect agreement of the presented theory with the experimentally verified perturbation model of thin strips is demonstrated.