SAW gas sensors are attractive because of their remarkable sensitivity due to changes of the boundary conditions (mechanical and electrical in the acoustoelectric effect) propagating of the Rayleigh wave, introduced by the interaction of a thin chemically active sensor film with gas molecules. This unusual sensitivity results from the fact that most of the acoustic wave energy is concentrated near the waveguide surface within approximately one or two wavelengths. In the paper a new theoretical

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... odel of analysing a SAW gas sensor is presented. The effect of SAW velocity changes depends on the profile concentration of diffused gas molecules in the porous sensor film. Basing on these analytical results, the sensor structure can be optimized. Some numerical results are shown.