Piezoelectric resonators for overtone oscillations

摘要

For the purpose of utilizing the characteristic in a vibration energy entrapping mode of a higher order symmetric or asymmetric mode vibration generated when a piezoelectric resonator is excited, there are provided a portion having a cutoff frequency f2 about an energy entrapping portion having a cutoff frequency f1 for strongly exciting a higher order symmetric or asymmetric mode vibration and at least one energy absorbing portion having a cutoff frequency f3 (at least f1 and f3<f2). The size of the energy entrapping portion (electrode), amount of plateback (f2-f1)/f2, the substrate thickness and a gap between the energy entrapping portion and the energy absorbing portion are selected such that the vibration energy of the overtone vibration whose orders are equal to or higher than the n-th overtone is substantially entrapped in a portion near the periphery of the energy entrapping portion, while the vibration energy of overtone vibrations of (n-2)th order or lower order including the fundamental vibration is caused to spread over the entire body of the substrate.