Patent ID: 8215561

Claim:
An antenna connectable to a reader-writer device configured to be communicatable with a wireless tag, the antenna comprising: a substrate made of a dielectric substance; and a conductor pattern formed on the substrate and including a feeding point at one end of the conductor pattern, via which the antenna is connectable to the reader-writer device, an open end at another end of the conductor pattern, a feeding-side extension part extending for a first predetermined distance from the feeding point, and a spiral part extending spirally in a spiral shape from an opposite end of the feeding-side extension part opposite to the feeding point to the open end being a terminal end of the spiral part, the spiral part including the open end and an open-end-side extension part positioned in juxtaposition with the feeding-side extension part, wherein a distance along length directions of the conductor pattern, from a zero point at which a current is zero in the open-end-side extension part upon feeding power to the feeding point, to an intersection point at which a virtual straight line perpendicular to the open-end-side extension part and passing through the zero point intersects the feeding-side extension part, is equal to or more than ¼ and equal to or less than ¾ of a wavelength of a radio wave used for the antenna.