RESONATOR FILTER DEVICE HAVING NARROW PASSBAND

摘要

PROBLEM TO BE SOLVED: To provide a filter device having a high coupling coefficient and narrow filter bandwidth characteristics.SOLUTION: A filter device 100 includes: series resonators 121-124 connected in series between an input terminal 110 and an output terminal 140; and shunt resonators 131-134 respectively connected between at least one of the series resonators and a ground voltage. Each of the series resonators and each of the shunt resonators have a corresponding parallel resonance frequency Fp and series resonance frequency Fs, respectively. At least one series resonator has a corresponding series resonance frequency Fs outside a range of a passband of the filter device, and at least one other series resonator has a corresponding series resonance frequency Fs within a range of the passband, and/or at least one shunt resonator has a corresponding parallel resonance frequency Fp outside a range of the passband of the filter device, and at least one other shunt resonator has a corresponding parallel resonance frequency Fp within a range of the passband.