The analysis of quasiacoustic‐wave excitation by the uniform interdigital transducer is approached from a field point of view. Fields within the transducer are expressed in terms of a set of normal‐mode functions which have been defined specifically for the interdigital array. Dispersion relations for these normal‐mode functions are found to display band‐gap regions with complex wave numbers. The complex wave number is responsible for the excitation process and permits a solution of the boundary conditions at both ends of the transducer structure. It is shown that the radiation fields excited by the transducer grow according to the dictates of a sine hyperbolic function from one end of the transducer to the other.
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