Phase-based Spatial Resolution of Chipless RFID Tags

We present a method for resolving multiple chipless RFID tags in a read zone using phase measurements conducted during a raster scan with a directive reader antenna. We differentiate between 3 chipless RFID tags with up to 2 shared resonance frequencies in the 3 - 4.4 GHz band, that are spaced as close as 6.4 cm apart. Furthermore, we automate the process of tag identification and location estimation with a positional error of less than 8 mm. We also present a relationship between tag resonant frequency and minimum tag spacing. Future directions are also discussed.