Shift of the Characteristic Frequencies of Thickness Mode Piezoelectric Resonators Caused by Intrinsic Losses and External Mechanical Load

Abstract

The effects of internal mechanical losses and external mechanical loading on the characteristic frequencies of thickness extensional piezoelectric resonators and transducers are investigated around the fundamental resonance. The exact one-dimensional model is used for the computation of the electrical input impedance. A complex elastic constant (c₃₃ ^D)* = c₃₃ ^D (1 + j tan δ_m) is used for the representation of mechanical losses. A constant Q model, with an attenuation linearly increasing with frequency, has been assumed for the piezoelectric material. External mechanical loads, represented by means of the characteristic impedances of the backing material and the irradiated media are normalized with respect to the characteristic impedance of the piezoelectric material.

Keywords:

• Thickness-extensional piezoelectric resonators
• piezoelectric transducers
• characteristic frequencies

Acknowledgement

This work was supported by the Spanish Ministry of Science and Technology. R&D Project DPI2002-00441.