Decoding of multiple same-coded in-line placed chipless RFID tags

In this paper, a technique to simultaneously decode multiple in-line placed and same-coded chipless radio-frequency identification tags is proposed. The methodology presented is valid for short range applications up to 1 m, and is based on the analysis of the received radar cross section of different sets of same-coded chipless tags, which makes the set identification independent of the distance to the reader. The received radar cross section increases directly proportional to the amount of chipless tags located within the reader´s interrogation zone. Several 3 bit chipless tags orientation independent and between the UWB frequency range from 3 to 6 GHz are fabricated using copper strips and commercial bond paper as a substrate. Up to 5 same-coded chipless tags placed in-line are successfully decoded at different distances from the reader, this enables the short range counting of same tagged objects. The technique is verified by simulation and measurements, confirming its viability to use the radar cross section to perform the multi decoding of same-coded chipless tags.