Influence of dimensions on the sensitivity characteristics of thickness extensional mode piezoelectric ultrasonic transducers

Abstract

If the thickness-to-width ratio of the thickness extensional mode piezoelectric ultrasonic transducer is not too large, the mode coupling will produce a complicated resonance system, and this will complicate the sensitivity characteristics, which is a basic characteristic of the ultrasonic transducer. If the dimensional ratio is adapted in such a way that the lateral mode can be suppressed, so the single mode of the thickness extension can be simplified, then the sensitivity characteristics of the ultrasonic transducer can be simplified. On the basis of lumped parameter equivalent circuit of the three-dimensional coupled piezoelectric transducer, the three-dimensional coupling sensitivity vs. frequency characteristics are derived, and the relationship between dimensional ratio and receiving sensitivity is clearly provided. From the frequency condition of the maximum sensitivity, the antiresonance coupling factor of the parallel longitudinal mode and, thus, the dimensional ratio condition of the mode simplification are derived. Furthermore, the degree of coupling with receiving sensitivity of parallel longitudinal mode is used as a measure to define the sensitivity coupling factor; and, based on the sensitivity coupling factor, the condition to simplify the sensitivity characteristics of ultrasonic transducer is shown.