Concentric Ring-Based Multibit Chipless RFID Tag

In this paper, a novel method is proposed to increase bit rate of concentric ring based chipless RFID tag. Three versions of concentric ring-based tags: ring type, slot type and combination of both are designed and their response in terms of number of resonant frequencies and identification (ID) bits are compared. The conventional ring type and slot type tags contain four concentric ring resonators and four slots respectively. Both conventional tags are uniplanar and produce 3 ID bits in the frequency range of 4-16 GHz. The proposed method is a combination of both conventional methods that means ring resonator on one side of substrate and complementary slots on the other side of substrate. Proposed tag produces 8 ID bits without increasing the physical size of tag. Three additional resonant frequencies are in lower frequency i.e., 2-4 GHz which makes the proposed tag compact compared to conventional tags.