Spectral theory of natural unidirectionality of SPUDT for B-G wave

A theory that exploits the Green´s function description of the elastic halfspace and the perturbation description of the mechanical properties of thin metal strips deposited on the halfspace surface is presented. The theory includes forward and backward propagating SAWs (surface acoustic waves) in the periodic system of strips which appear in the solution of a suitable eigenvalue problem. The solution of an electrically inhomogeneous problem that describes the SAW generation and detection properties of elastic and perfectly conducting strips is given. The final result of the theory is a comprehensive model for a one-strip section of a system of strips that can be easily applied in analysis of nearly periodic interdigital transducers with a finite number of electrodes. The model is applied in the analysis of an NSPUDT (natural single-phase unidirectional transducer)