Improving transducer performance using multiple active layers

The performance of a transducer possessing several piezoelectric layers is discussed. Techniques are presented for determining excitation functions so that a pre-defined transmission characteristic is obtained in an optimal manner. The performance of a multiple layer transducer in the reception mode is considered in detail. It is evident that a high degree of transmission and reception efficiency is attainable continuously from below the fundamental thickness mode resonance to above its third harmonic. This contrasts with conventional designs which possess a null at the second harmonic. Issues regarding the stability of the technique are addressed.