Patent ID: 8618995

Claim:
A wireless tag, comprising: a power feeding unit to feed electric power in order for a metal pipe to function as an antenna, the power feeding unit being placed inside the metal pipe that is formed with a slot having a predetermined length in a longitudinal direction, and including conductor pattern taking an arc shape along an inner periphery of the metal pipe, the conductor pattern being isolated from the metal pipe and for feeding the electric power to the metal pipe through electromagnetic coupling; an IC (Integrated Circuit) chip, which is placed inside the metal pipe and is connected to the power feeding unit, to allow monitoring of position of the metal pipe that is a construction material; and a matching unit including a looped conductor pattern formed in parallel with a plane orthogonal to the longitudinal direction and connected to the IC chip in parallel with the looped conductor pattern, the matching unit to take impedance matching between the metal pipe and the IC chip, wherein the frequency of the electric power is lower than the cutoff frequency of the metal pipe.