A spectrally efficient chipless RFID tag based on split-wheel resonator

A completely passive, compact and fully printable chipless RFID tag is proposed. The tag utilizes the scattering from an array of orthogonally polarized split-wheel resonator pairs to achieve multi-bit data capacity. As split-wheel resonators of identical resonance frequency but with orthogonal polarizations do not interfere with each other in their first mode of resonance, this allows realization of the same frequency band twice, once for each polarization, to encode information, thus enhancing the overall spectral efficiency of the proposed tag. When interrogated with broadband plane wave signals of two orthogonal polarizations, the reader detects the RCS peaks generated by each of the resonator pairs in both x- and y-polarizations and with n resonator pairs, effectively 2²ⁿ-1 items can be tagged and identified. As the tags require only single sided metallization, direct printing of such tags using conductive ink on paper or polymer substrate can yield a ubiquitous electronic tagging method which can replace optical barcode in the future.