Patent ID: 7876190

Claim:
A double-tuned circuit comprising: a primary side tuned circuit having a first air-cored coil; a secondary side tuned circuit having a second air-cored coil; wherein the first air-cored coil and the second air-cored coil are opposed to each other so that one opening end of the first air-cored coil and one opening end of the second air-cored coil are capable of being coupled to each other on a coil mounting surface; wherein the coil mounting surface is provided with a first conductive pattern formed adjacent to the first air-cored coil in a direction perpendicular to an arrangement direction of the first and second air-cored coils, and both ends of first conductive pattern are connected to a ground; wherein the coil mounting surface is provided with a second conductive pattern formed adjacent to the second air-cored coil in the direction perpendicular to the arrangement direction of the first and second air-cored coils, and both ends of the second conductive pattern are connected to the ground; wherein the first conductive pattern extends from a first ground pattern formed close to the other opening end of the first air-cored coil to a side of the first air-cored coil on the coil mounting surface; wherein the second conductive pattern extends from a second ground pattern formed close to the other opening end of the second air-cored coil to a side of the second air-cored coil on the coil mounting surface; and wherein the extending ends of the first and second conductive patterns are connected to one end of the first air-cored coil close to the ground through a third conductive pattern.