Evaluation of finger withdrawal transducer admittances by normal mode analysis

Nonnal mode analysis is combined with the complex Poynting theorem to derive the admittance of unapodized interdigital surface acoustic wave transducers. The formulation expresses the admittance in terms of integrals over the electric potential of the transducer. With out specification of the form of the transducer, the Hubert transform relation between real and imaginary parts of the admittance is demonstrated. Simple formulas are derived for the midband radiation conductance of a transducer which has had electrodes removed to alter its band shape.