Patent ID: 6989726

Claim:
A high-frequency filter circuit comprising: a first coupled transmission line section having an input side first line whose one line end serves as an input port and an other line end serves as an open end, an input side second line and an input side third line, which are arranged on either side of the input side first line; and a second coupled transmission line section having an output side first line whose one line end serves as an output port and an other line end serves as an open end, an output side second line and an output side third line, which are arranged on either side of the output side first line, the input side second line having an open end at a line end located on same side as that of the open end side of the input side first line, the input side third line having an open end at a line end located on same side as that of the input port side of the input side first line, the output side second line having an open end at a line end located on same side as that of the open end side of the output side first line, the output side third line having an open end at a line end located on same side as that of the output port side of the output side first line, a line end located on the input port side of the input side second line of the first coupled transmission line section being connected to a line end located on the side opposite from the output port side of the output side third line of the second coupled transmission line section, and a line end located on the output port side of the output side second line of the second coupled transmission line section being connected to a line end located on the side opposite from the input port side of the input side third line of the first coupled transmission line section.