PIEZOELECTRIC RESONANCE FILTER HAVING FREQUENCY CHARACTERISTIC EXHIBITING LOW AND HIGH FREQUENCY ATTENUATION EXTREMA AND DUPLEXER

摘要

PURPOSE: A piezoelectric resonance filter having a frequency characteristic exhibiting low and high frequency attenuation extrema and a duplexer is provided to prevent defects due to a variation of a band of a filter corresponding to a variation of temperature in a process for restraining reduction of bandwidth. CONSTITUTION: A piezoelectric resonant filter includes a plurality of thin-film piezoelectric resonators. Each of the thin-film piezoelectric resonators includes a piezoelectric thin film(15) having a piezoelectric characteristic and a pair of excitation electrodes(14, 16) disposed on opposite surfaces of the piezoelectric thin film to apply an excitation voltage to the piezoelectric thin film. A variation rate of frequency corresponding to a temperature variation of a first frequency at the low frequency attenuation extremum is different from a variation rate of frequency corresponding to a temperature variation of a second frequency at the high frequency attenuation extremum.