Patent ID: 8289103
Filing Date: 2012-10-16
Classification: H03H

Abstract:
1. A filter device comprising a first terminal and a second terminal, the filter device comprising: a reactance element connected between the first terminal and the second terminal; a first serial resonance circuit connected between a connection point connecting the first terminal and one end of the reactance element, and a ground, the first serial resonance circuit including a first inductor and at least one first capacitor connected in series via respective connection points for connecting the first inductor and at least one first capacitor; a second serial resonance circuit connected between a connection point connecting the second terminal and the other end of the reactance element, and the ground, the second serial resonance circuit including a second inductor and at least one second capacitor connected in series via respective connection points for connecting the second inductor and at least one second capacitor; and a third capacitor connected between one of the respective connection points of the first serial resonance circuit and one of the respective connection points of the second serial resonance circuit, wherein one of the first, second, and third capacitors is a variable capacitive element, wherein the variable capacitive element is connected to the first terminal via at least the first capacitor of the first serial resonance circuit, and is connected to the second terminal via at least the second capacitor of the second serial resonance circuit, wherein the filter device comprises a controller for controlling two attenuation pole frequencies of the filter device by changing a capacitance of the variable capacitive element, wherein the third capacitor is the variable capacitive element, and wherein one end of the variable capacitive element is connected to the first terminal via at least the first capacitor of the first serial resonance circuit, and the other end of the variable capacitive element is connected to the second terminal via at least the second capacitor of the second serial resonance circuit.