According to an embodiment of the invention, a coupler has a first line that includes a coiled main line and a second line that includes a coiled secondary line arranged to oppose the main line via an insulating layer. The coupler also has a plurality of vias that connect the separate portions of the first line arranged in the different layers and connect the separate portions of the second line arranged in the different layers, and a plurality of terminals each connected to an end of the first and second lines. The vias include an extension via connected to the main line or the secondary line that extends through the insulating layer, and the extension via wires the first line and the second line to the same side of the insulating layer.