Antenna device, radio tag reader and article management system

摘要

There is provided with an antenna device includes; a first antenna element which is either a spiral antenna element or a loop-like antenna element; and a first feed point provided at a first end of the first antenna element, the first end being an outer end of the spiral antenna element or an one end of the loop-like antenna element, wherein a length from an second end of the first antenna element to the first end of the first antenna element along the first antenna element is about one half wavelength of operating frequency, the second end being an inner end of the spiral antenna element or the other end of the loop-like antenna element.