Patent ID: 8847700

Claim:
A filter, comprising: a filter circuit having a prescribed passband and including: a plurality of series resonators; and a plurality of first parallel resonators; and an impedance matching circuit including: a second parallel resonator; and an inductance that is connected in series to the second parallel resonator, wherein the second parallel resonator is connected in parallel to at least one of the plurality of first parallel resonators that has no inductance connected thereto without any one of the plurality of series resonators interposed therebetween in a series arm to which the second parallel resonator and said at least one of the plurality of first parallel resonators are connected, wherein an antiresonance frequency of the second parallel resonator in the impedance matching circuit is equal to or higher than an antiresonance frequency of at least one of the series resonators and is equal to or higher than a highest frequency of the prescribed passband of the filter circuit, wherein a resonance frequency of the second parallel resonator in the impedance matching circuit is shifted by the inductance so that a resonance frequency of the impedance matching circuit is equal to or lower than a resonance frequency of at least one of the first parallel resonators and is equal to or lower than a lowest frequency of the prescribed passband of the filter circuit.