Analysis of frequency response characteristics of polymer ultrasonic transducers

Piezoelectric polymers have large dielectric and mechanical internal losses. In this study, we introduced internal losses into Mason's equivalent circuit, and analyzed the effects of these losses on the transducer response, mainly in the frequency domain. To prove the validity of the theoretical analysis, we fabricated polymer transducers of several backing load types which are effective for practical use, using vinylidene fluoride and trifluoroethylene copolymer films, and evaluated their frequency and impulse responses. The experimental results are in good agreement with the theoretical prediction. We conclude that a consideration of the internal losses is essential for the proper design and correct evaluation of polymer transducers.