Theoretical model for ball surface acoustic wave (SAW) sensors has been developed. Wave front distortion encountered in planar SAW sensors caused by diffraction or reflection can be neglected because of the diffraction-free propagation of a naturally collimated beam. Wave form at each turn is expressed by an integral of terms defined by the array factor and the elementary charge density of electrodes as well as the frequency-dependent velocity and attenuation caused by the sensitive film. Irrespective of the significant simplicity of the theory, excellent agreement has been observed between the simulated and experimental wave forms of a double-electrode ball SAW sensor.
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