Patent ID: 7170370

Claim:
A filter device which is constituted by circuit elements formed on a single substrate, said circuit elements comprising: a first wiring section which is formed between an input signal electrode and an output signal electrode; at least one first resonator which is located in said first wiring section and which has a predetermined resonance frequency; at least one second wiring section which is toned between said first wiring section and a ground electrode; a second resonator which is located in said second wiring section and which has an and-resonance frequency forming a pass-band with said predetermined resonance frequency of said at least one first resonator; and an effective electric and mechanical coupling factor of at least any one of said first and second resonators being different from those of the other resonators, wherein a plurality of said second resonators are located in said second wiring sections, the effective electric and mechanical coupling factor of a part of said second resonators being different from those of the other said second resonators and said first resonator, wherein the part of said second resonators has a value of the effective electric and mechanical coupling factor different from those of the first resonator while the other said second resonators have the same value thereof as those of the first resonator, an impedance of the part of said second resonators being made lower than those of the other said second resonators.