PIEZO ELECTRIC RESONATOR AND PIEZOELECTRIC FILTER USING THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a piezoelectric resonator with a small impedance that is less affected of spurious vibration and to obtain a piezoelectric filter with a wide pass band that has a small ripple component in the pass band caused by the effect of the spurious vibration of the piezoelectric resonator. SOLUTION: The piezoelectric resonator 10 includes a substrate 12. A vibration section 20 consisting of a dielectric thin film 14, a couple of electrode thin films 16 and a piezoelectric thin film 18 is formed on the substrate 12. The n-th mode of thickness longitudinal vibration or thickness share vibration is applied to the piezoelectric resonator 10. A condition of r>=20 t/n holds, where r is the radius of a part opposite to the electrode thin film 16 and t is the thickness of the vibration section 20. By connecting the piezoelectric resonators 10 above in a ladder form the piezoelectric filter is formed.