Orientation Independent Chipless RFID Tag Using Novel Trefoil Resonators

Abstract

In this paper, a compact and fully passive bit encoding circuit, capable of operating as a chipless radio frequency identification (RFID) tag is presented. The structure consists of novel concentric trefoil-shaped slot resonators realized using Rogers RT/duroid R 5880 laminate, occupying a physical footprint of 13.55 × 13.55 mm 2. Each resonating element is associated with a particular data bit, having a 1:1 resonator-to-bit correspondence. Bit sequences are configured through introducing modifications in the geometric structure either by addition or exclusion of each nested slot resonator. Such changes manifest directly in the electromagnetic signature of the tag as presence or absence of corresponding resonant peaks. The proposed 10-bit tag offers minimized inter-resonator mutual coupling and insensitivity to changes in polarization and incident angles thereby demonstrating orientation independent functionality. Moreover, error-free encoding is achieved through stabilizing the shift in resonant frequencies for a variety of different geometric configurations and orientation of the structure. The tag operates within the license-free ultrawideband ranging from 5.4 to 10.4 GHz, providing spectral bit capacity and bit density of 2 bits/GHz and 5.44 bits/cm 2 respectively. INDEX TERMS Chipless tag, on-off keying (OOK), radar cross-section (RCS), radio frequency identification (RFID).

Data-Dense and Miniature Chipless Moisture Sensor RFID Tag for Internet of Things

“…The current distribution of the above-mentioned tag at the smallest frequency of 4.1 GHz is shown in Figure 5(a). It is depicted that the maximum concentration of current is present around the top and bottom side of the slot resonator representing inductive effects, while the minimum density of current is situated around the left and right edges of the slot indicating capacitive effects [32]. The current distribution of the above-mentioned tag at the smallest frequency of 4.1 GHz is shown in Figure 5(a).…”

Chipless RFID Reading Method Insensitive to Tag Orientation

“…In practice, these conditions can be satisfied for every structure having a rotational symmetry (which include, triangle, square, pentagon, circular patterns...) [15]. This idea has been applied, even if not clearly stated, in [5]- [7] where authors have designed circular chipless tags and in [4], [8], where triangle, hexagonal and trefoil-shaped resonators have been used. All the mentioned tags are read in co-polarization, and do not have any cross-polarization (as predicted by the presented model).…”

“…Orientation is also a key challenge since for most of RFID chipless systems, tag's orientation has to be known by the reader before the interrogation. Considerable effort has been put into the tag design to overcome this limitation both in co-polarization [4]- [8] and cross-polarization [9], [10], but few papers have addressed this problem from the reader side [11], [12].…”

High-Q Slot Resonator Used in Chipless Tag Design

“…H less tags have shortcomings in terms of data capacity and tag size [7]. In recent decades, many researchers have proposed various types of which are divided into two categories: time-domain (TD) [8][9][10][11][12][13], and frequ (FD) chipless tags [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] The Ref. [8] proposed a near-field chipless tag system with sequential r time domain.…”