Passive Orbital Angular Momentum RFID Tag based on Dielectric Resonator Arrays

In this paper, a novel approach is proposed to increase the information content of RFID tags using uniform helically arranged spherical dielectric resonator arrays. The proposed tag design is scalable to operating frequency in the mm-wave/THz range and provides a larger information content due to new additional values per digits according to the excited OAM modes $(m_{n}=\ldots,-2,-1,0,1,2,\ldots)$ instead of the binary values ( $b_{n}=0$ and 1). This new values can be called OAM values. By means of the orbital angular momentum (OAM) concept three uniform helically arranged spherical dielectric resonator arrays operating at three different frequencies $f_{1}=10\ \text{GHz},\ f_{2}=10.5$ GHz, and $f_{3}=11\ \text{GHz}$ are established to provide a $m_{1}m_{2}m_{3}$ 3-digits OAM coded tag. Each array consists of 8 dielectric resonators (DRs) with three different radii in order to enhance the isolation between the different arrays. The OAM mode orders are generated by the interaction of phase delayed radiation from each DR element in the array. Each DR element is elevated in order to achieve the right phase shift, which is related to the mode order, the number of elements, and the propagation wavelength. Two examples of 3-digits OAM coded tags with the code −110 and −210 have been simulated and compared with a $b_{1}b_{2}b_{3}$ 3-digits conventional coded tag with the code 111 in order to compare the two approaches.