2-D Localization of Radio Frequency Identification Tags From Measurements of the Weighted Integrals of the Magnetic Flux Density

This paper presents a novel method for the localization of a passive radio frequency identification (RFID) tag in a 2-D space. First, we show that the position of the tag can be estimated as the intersection of two orthogonal lines, which are determined by the weighted integrals of the magnetic flux density created by the tag. To measure them, we developed a square magnetic sensor composed of six coils: four rectangular coils, a set of four bow-tie-shaped coils connected in series, and a square coil. Using this sensor with side lengths of 200 mm, an RFID tag was localized in a 180 mm square domain with an average error of 5.1 mm. Using the sensor with side lengths of 400 mm, the RFID tag was also localized in a 300 mm square domain with an average error of 1.8 mm.