PT Unknown
AU Alhaj Abbas, A
TI Dielectric Resonator-Based Passive Chipless Tags for Identification and Ranging
PD 11
PY 2020
DI 10.17185/duepublico/73131
LA en
AB Wireless identification and sensing based on the backscattered electromagnetic field have recently attracted much interest in a wide spectrum of applications under the umbrella of the RFID technology. Dielectric resonators (DRs) have recently shown the potential to be used as chipless RFID tags and sensors. One of the RFID applications, in the focus of this dissertation, is an indoor self-localization system where a smart object uses the backscattered signals of reference DR tags to localize itself. The major challenge that impedes the efficient operation of such systems is the low RCS of the DR, which severely limits the reading range of the tag and complicates the detection of the tags in a cluttered environment. Therefor, the contribution of this dissertation is twofold: modelling the scattering of the DR tag, and designing enhanced RCS tags with identification or sensing capability based on combining the DR with a dielectric lens. First, we study the transient scattering behaviour of the DR, which describes the relationship between the pulse length of the excitation signal and the peak scattering magnitude. This study allows us to give a first estimate to the structural mode scattering by exciting the DR by a very short pulse. A further investigation on the mono-static RCS spectrum leads to describe the structural mode scattering magnitude and phase spectrum by a circuit model. Second, the concept of enhancing the RCS of the DR tag is realized by placing a single DR in the focal area of a dielectric lens. RCS enhancement is found to vary with the modes of the DR but increases approximately with the fourth power of the lens radius. Based on the lens-DR combination, we propose two novel RFID tag designs: wide-angle tag and Angle of Arrival (AoA) sensing tag. The first design is constructed of the combination of several DRs of the same dimensions with a dielectric spherical lens. We show by simulation and experiments that a set of 5 to 6 different tags can be discriminated by their resonant frequencies unambiguously over +/- 50° of incidence angle of the reader signal. In the second design, we combine the lens with different size DRs, which exhibit resonant frequencies separated by large frequency gaps. Simulated signatures of a lens of 120-mm diameter with seven spherical DRs are presented, and results are supported by experiment. Correlation processing of the signatures can give a resolution of few degrees in AoA.
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