A new model for the flat conductor electromagnetic SAW transducer

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Abstract
Previous models for Rayleigh- and Lamb-wave electromagnetic transducers have been based on the assumption that the current distribution in each transducer conductor is uniform. We present solutions for the dynamic magnetic fields surrounding an array of flat conductors above a ground plane in which the current distribution is allowed to vary. The resulting solutions are used to calculate space-harmonic curves and to derive a new transducer model including electrical inductance, eddy current resistance, acoustic impedance, and transducer efficiency. A direct analogy to the interdigital transducer is established. For fundamental frequency operation, this model is nearly equivalent to previous flat field models, provided the conductor width/spacing ratio is 1/2 or less. For harmonic transducer operation, the present analysis is substantially different from other models and it matches data more accurately. A method for measuring the individual insertion loss of dissimilar transducers in a lossy medium is presented.