Patent ID: 7414497
Filing Date: 2008-08-19
Classification: H03H

Abstract:
1. A piezoelectric thin-film filter comprising pluralities of first, second, and third resonators, each resonator comprising a pair of electrodes sandwiching a piezoelectric thin film, wherein the second resonators or the first and third resonators connected in parallel are disposed so as to constitute series-arm resonators or parallel-arm resonators connected in a lattice pattern, wherein the capacitance of each of the second resonators is larger than the capacitance of each of the first resonators, wherein the capacitance of each of the third resonators is substantially equal to the difference between the capacitance of any one of the second resonators and the capacitance of any one of the first resonators, wherein the resonant frequency of each of the first resonators is higher than the resonant frequency of each of the second resonators, and wherein the anti-resonant frequency of each of the third resonators is higher than the resonant frequency of each of the second resonators and lower than the resonant frequency of each of the first resonators.