A New Detection Method for Sub-Harmonic Components Using a Double-Layered Piezoelectric Transducer

A new system for detecting the sub-harmonic component of ultrasonic pulse wave is constructed. Double-layered piezoelectric transducer (DLPT) [1] which has the identical polarization directions is for the detection. The resonance frequency of the DLPT comprised of two transducers (with resonance frequency of f) is equal to f when the transducers are electrically connected in parallel and to f/2 when the transducers are connected in series connection. The performance of the DLPT used in this ultrasonic system is described. As the experimental results, the efficient detection of the sub-harmonic component of the ultrasonic pulse wave reflected by a reflector is successfully accomplished. On contrary, the sub-harmonic component could not be detected by using conventional system without an electrical switch for elctrical connection of the DLPT.