Encoding Strategy to Increase the Data Capacity in Near-Field Chipless-RFID Systems

In this paper, we propose a novel encoding strategy for chipless-RFID systems based on near-field coupling and sequential bit reading, where the bits are read synchronously. The main purpose of this encoding strategy is to increase the data density per unit length (DPL) and surface (DPS) of the tags, as compared to those data densities achievable with a conventional encoding scheme. Such new encoding uses both the rising and falling edges of a clock signal, generated by the motion of the tag over the sensitive part of the reader. Experimental validation is demonstrated by fabricating and reading two 19-bit tags. Such tags consist of two chains of rectangular metallic patches, whereas the sensitive part of the reader is based on a microstrip transmission line loaded with two different and uncoupled complementary split ring resonators (CSRRs).