Abstract
The behavior of a piezoelectric transducer with a very high electromechanical coupling coefficient close to 1 was analyzed in three steps: intuitive modeling, analytic solution using a 1D model, and numerical simulation using a finite element code. The results were then compared with those from a conventional transducer using PZT, which confirmed that a high coupling coefficient should be utilized to enlarge the bandwidth of the transducer rather than only to increase the sensitivity. The intuitive modeling showed that a piezoelectric transducer with shunt electrodes behaved in a softer manner than with open electrodes. This is equivalent to the fact that the frequency minimizing the electrical impedance of the transducer (resonant frequency) is reduced from the frequency maximizing the electrical impedance (anti-resonant frequency) by the piezoelectricity, and explains why the very high coupling coefficient close to 1 can lead to the wide bandwidth of the transducer.
