A Space-Frequency Technique for Chipless RFID Tag Localization

In this paper, a new technique is proposed for the accurate localization of chipless RFID tags presented in the reader area. The reader area is subdivided into some triangular unit cells. Each unit cell is covered by three antennas located at the vertices of the triangle in order to extract the positions of the tags. Assuming the reader area as the scatterer medium, the tags act as the scattering centers of the medium. Employing some mathematical description, it is shown that by applying the narrow-frequency matrix pencil method (NFMPM) to the frequency response of the tag, the distance of the tag from the antennas can be found from a space-frequency diagram. Having three distances and coordinates of the antennas, the position of the tag can be obtained easily by triangulation technique. Different scenarios are simulated and validated with the measured results. The measured range and angle errors achieved based on the proposed approach are less than 1.5 cm and 2.6 ^° for a tag with area of 15 × 25 mm².