Patent ID: 7138888

Claim:
A filter comprising: a series piezoelectric resonator part including at least one series piezoelectric resonator having electrodes, the series piezoelectric resonator being connected in series between an input terminal of the filter and an output terminal of the filter; a parallel piezoelectric resonator part including at least two parallel piezoelectric resonators each having a first electrode and a second electrode, the parallel piezoelectric resonators being connected, via the first electrodes, in parallel to the series piezoelectric resonator and in a ladder configuration; an inductor part including inductors having electrodes, the inductors being provided to at least two of the parallel piezoelectric resonators, respectively, the inductors each connecting between a ground and the second electrode of the respective parallel piezoelectric resonator; and an additional piezoelectric resonator part including at least one additional piezoelectric resonator having a first electrode and a second electrode, the first and second electrodes being respectively connected to the second electrodes of any two of the parallel piezoelectric resonators having the inductors connected thereto.