ANALYSIS OF DOUBLE-EXCITED PIEZOELECTRIC TONPILZ TRANSDUCER

The piezoelectric Tonpilz transducer has many obvious advantages, such as simple structure, high electro-acoustic transforming efficiency, and high transmitting power. Its usefulness is limited because of its high mechanical quality factor Q. Transducer of Tonpilz type with double excitations has been invented to broaden the operating frequency band by stimulating two adjacent longitudinal vibration modes. However, the peak and valley level of transmitting voltage response (TVR) was hard to be less than 3dB without matching layers. Modulation of the added mass in the pzt-4 ceramics helps get near the first two longitudinal resonant modes, while the length and radiating area of head plate influence the bending modes and radiation quality factor. Double-excited tonpilz transducers which combine the first two longitudinal modes and bending modes were designed with the help of finite element software. By stimulating no less than 3 vibration modes, the -3dB operating bandwidth was much broader than ever before, what's more, the performance achieved without the help of matching layers.