Second harmonic imaging transducers

摘要

A harmonic imaging transducer is a structure of two mechanically coupled piezoelectric layers. This two-layer piezoelectric structure may vibrate either in a symmetric mode, wherein the two layers are expanding and contracting in unison, or in an anti-symmetric mode, wherein one layer is contracting while the other is expanding. Symmetric mode vibrations result in first harmonic operation, while anti-symmetric mode vibrations result in second harmonic operation.