Design of Chipless RFID Transponders for Retail and Healthcare Applications

Abstract

Chipless radio frequency identification (RFID) is a low-power, non-line-of-sight wireless technique that has the potential to regulate the automatic identification (Auto-ID) industry with its various applications in healthcare, automated identification, object tracking, security, and authentication with less human intervention. Chipless RFID is fundamentally an alternative solution to conventional high-frequency (HF) or ultrahigh-frequency (UHF) RFID. Numerous industries, including fare collection, item monitoring, road tolls, and medical applications, heavily rely on RFID technologies. Businesses are becoming increasingly interested in such a new and promising technology because of characteristics like orientation independence, large storage, low cost, a large detection range, robustness to ambient conditions, and the non-intervention of human labour. This dissertation aims to investigate whether chipless planar microstrip resonators can be successfully applied to the physical layer of a chipless RFID system. To reduce the cost of a passive tag, we must not only increase the coding capacity of resonator-based tags but also limit their overall dimension using an inexpensive substrate by ensuring that the control structures won't harm the system's performance. The major goal is to investigate various resonator types and how they might be used to compact passive RFID transponders for use in retail and healthcare utilities using inexpensive substrates like FR4. In this research work, a range of resonators, from 1-bit to 15-bit transponders, are analyzed using rectangular, modified rectangular, square, octagonal, split-ring, complementary, and hybrid resonators. This study suggests innovative design choices to miniaturize passive transponders that combine a hybrid design with stepped impedance resonators (SIR) and rectangular stub resonators. By removing constraints including cost, size, and coding capacity, the analysis seeks to help the development of chipless RFID technology progress. With a physical footprint of 32 mm × 15 mm and a maximum radar cross-section (RCS) response of -25.66 dBsm, the design is guaranteed to have a 10-bit coding capacity. The RCS response has been examined at the receiver using a rectangular windowing approach, which improves the RFID system's coding capabilities and security characteristics. Additionally, Hamming, Hanning, and Bartlett windows are used and evaluated to demonstrate the efficacy of windowing approaches in RFID coding. To increase detection accuracy, the performance of the tag is examined at various tilt-angles and read distances. A reference wideband horn antenna is used as the interrogator to study the tag detection procedure, having gains of 6.6 dBi and 18.77 dBi at 0.5 GHz and 5.8 GHz, respectively. The measurements are carried out in a bistatic mode, and the outcomes employing frequency domain analysis with a maximum radar cross-section of -15 dBsm justify the 15-bit coding capacity of the chipless tag. A multi-narrow band chipless RFID reader antenna based on a modified rectangular resonator is also analyzed. The reader antenna is fabricated and measured to validate multiple narrowband behaviours. The measurement results show that the reader antenna can detect 11-bit multi-frequency coded chipless tags and depict gains of 4.7 dBi and 5.2 dBi at 0.58 GHz and 2.4 GHz, respectively. The cubic interpolation approach as a signal processing technique is applied at the reader end to eliminate the unnecessary drops at the measurement. Further study of the fundamental limit demonstrates that the physical dimensions of the proposed antenna and the radiation characteristics fulfil the dimension’s criteria. The multiple narrow-band responses of the reader antenna can be suitable to detect multi-bit tags, which are of high demand because a multi-bit transponder can be used for multiple frequency applications for hassle-free wireless environments, viz. tracking, retailing, identification, and healthcare utilities.