Patent ID: 9509279
Filing Date: 2016-11-29
CPC Classification: H03H

Claim Text:
1. A filter device comprising: an input terminal; an output terminal; a line connecting the input terminal and the output terminal; a first LC parallel resonance circuit connected between the line and a ground potential and including a first inductance; a second LC parallel resonance circuit connected between the line and the ground potential and including a second inductance; and at least one elastic wave resonator connected between an end portion of the first LC parallel resonance circuit at a line side and an end portion of the second LC parallel resonance circuit at the line side; wherein the first and second LC parallel resonance circuits are electrically coupled by a capacitive property of the at least one elastic wave resonator; attenuation-frequency characteristics of an LC filter defined by the first and second LC parallel resonance circuits and the capacitive property of the at least one elastic wave resonator, and attenuation-frequency characteristics defined by an anti-resonance point of the at least one elastic wave resonator are combined; and the first inductance included in the first LC parallel resonance circuit and the second inductance included in the second LC parallel resonance circuit are magnetically coupled.