2017 Volume 14 Issue 10 Pages 20170243
A polarization insensitive, compact, fully-passive bit encoding structure exhibiting 1 : 1 resonator-to-bit correspondence is presented. Inspired by frequency selective surface (FSS) based microwave absorbers, the structure readily operates as a chipless radio frequency identification (RFID) tag. The unit cell is composed of several concentric hexagonal loops. Finite repetitions of the unit cell constitute the proposed RFID tag in its entirety. The required bit sequence is encoded in the frequency domain by addition or omission of corresponding nested resonant elements. A functional prototype is fabricated on a commercial-grade grounded FR4 substrate, occupying a physical footprint of 23 × 10 mm2 while offering a capacity of 14 bits. The proposed tag boasts a minuscule profile, and demonstrates polarization insensitivity as well as stable oblique angular performance.