Patent ID: 7782157

Claim:
A resonant circuit comprising: an input transmission line; an output transmission line of which an input terminal is connected to an output terminal of the input transmission line; a first capacitor of which one terminal is directly connected to an input terminal of the input transmission line and the other terminal is directly connected to an output terminal of the output transmission line; a main resonant portion of which only one terminal is connected to both the output terminal of the input transmission line and the input terminal of the output transmission line; a second capacitor of which one terminal serves as an input terminal and the other terminal is connected to the input terminal of the input transmission line; and a third capacitor of which one terminal is connected to the output terminal of the output transmission line and the other terminal serves as an output terminal, wherein the main resonant portion comprises a transmission line which is grounded through a fourth capacitor and disposed at a terminal portion of the main resonant portion.