Polarimetric Radar Barcode: A Novel Chipless RFID Concept With High Data Capacity and Ultimate Tag Robustness

This paper presents a novel chipless radio frequency identification (RFID) concept where the information is encoded on the tag with a 2-D polarimetric radar barcode. We achieved a data capacity with this technique that is outstanding for chipless RFID. Even though these chipless RFID tags are simple, they are extremely robust in harsh environments. The polarimetric radar barcode is formed by a set of geometric structures like small dihedral mirrors, plane surface elements, or dipole elements with different polarimetric backscattering behaviors. These structures are arranged in a 2-D array to create a specific polarimetric 2-D radar barcode. The information is read by polarimetric millimeter-wave imaging radar. The lateral resolution of the radar determines the minimum resolvable element size and is therefore critical for the maximum data capacity of the tag. We show that, theoretically, a data capacity of more than 800 bit on a surface less than the size of a credit card can be achieved if a millimeter-wave multiple-input multiple-output radar is used as reader. The polarimetric encoded reflectors can be formed by metal or reflecting ceramic structures, and the tag can consist of a single material. Thus, tag robustness is limited only by the robustness and temperature resistance of the material used. We verify the performance and functionality of the proposed chipless RFID concept with measurements taken in a laboratory test setup with a 20-bit tag and a millimeter-wave radar system with 77.5-GHz center frequency.