GENERAL EQUIVALENT CIRCUIT OF PIEZOELECTRIC TRANSDUCERS VIBRATING IN THICKNESS MODES.

Thickness vibrations of a thin piezoelectric plate with mechanical loads on major surfaces are analyzed in two cases: 1) perpendicular field excitation caused by electrodes on both major surfaces; and 2) parallel field excitation caused by electrodes on side surfaces. Transducer characteristics are represented by equivalent circuits having seven ports, one of which is for electrical terminal, with three each for mechanical terminals on both major surfaces. The result is a generalization of previous analyses for the case of resonators without mechanical load and includes, as a special case, Mason's equivalent circuit. This circuit is applicable to a simple transducer, in which one and only one plane wave is excited by perpendicular field.