To provide an antenna which makes a base part of a helical antenna electromagnetically approximate a transmission line feed on a surface of a substrate and includes a three-dimensional shape section of a flex circuit.

The present invention relates to a helical antenna including a section of a microstrip of an antenna feed segment on a surface of a substrate, a generally cylindrical support core that conforms with the shape of the helical antenna and is held at a predetermined position on the substrate, and a conductor of a flex circuit in a comparatively thin ribbon shape of dielectric coating. The conductor includes a first segment of the conductor fixed by being adhesively wound around an outer surface of the core in order to form a decal-like helical antenna winding wire on the core, and a second segment of the conductor fixed generally in a lower area of a plane in a base part of the core at a position of the conductor for electromagnetic coupling in proximity with a portion of microstrip feed at a predetermined position on the substrate.