Collision, Data Recovery and Localisation in Chipless RFID
Creators: name: Rubayet-E-Azim
Publisher: name: Monash University
Year: 2022
Subjects: Electrical engineering not elsewhere classified

description: Radio Frequency Identification (RFID) is a disruptive and most discussed technology in recent decades. Near field communications (NFC), keyless access and car immobilisers are some potential applications of RFID. Due to the high cost of tags, many ambitious projects such as the mandates of Walmart and the Department of Defense (DoD), USA to implement the RFID technology in supply chain management were stalled. Besides tag cost, other impediments are incompatibility of direct printing on packaging materials like optical barcodes, and unsustainability of silicon chips in extreme environments. Chipless RFID becomes a prominent research to address the above issues of the cost of the tag and sustainability. Fully printable chipless RFID tags are void of any intelligence due to the absence of the application specific integrated circuit (ASIC) microchip. Due to the dumb tags, the reader performs all signal processing tasks. These new requirements have opened up the new field of research in the chipless RFID signal processing. The thesis has addressed this needs with the research of anti-collision, data recovery and localisation of the chipless RFID. <br> Four different types of backscattering, frequency domain chipless tags have been designed, fabricated, tested and analysed for their theoretical and experimental maximum detection ranges and backscattered radar cross section (RCS) levels. These tags are used to validate the proposed algorithms for collision detection, ranging and data recovery. Three new collision detection and data recovery signal-processing algorithms are proposed and validated in this research. They are: i) Resonance Localisation in time-frequency plane, ii) Fractional Domain Analysis (FrFT) and iii) Continuous Wave (CW) Method. The first method is based on time-frequency analysis of collided tag response for data recovery. This method is a two-level algorithm. The first level detects the collision through a correlative signal processing approach. The second level makes the data recovery by analysing the collided signal in time-frequency plane through Short Time Fourier Transform (STFT). The second method analyses the collided response signal in a fractional domain where multiple tag responses are localised as impulse like response at different index positions. This is also a two-level algorithm. The fractional domain analysis is the first level where a collision is detected together with the number of collided tags. The second level is separating them through windowing and analysing them separately in the frequency domain for data recovery and identification. The third method is the CW method inspired from continuous wave radar. Here the tags are interrogated through a continuous linear frequency modulated the signal. The received signal from the interrogation zone is mixed to generate an intermediate frequency signal (IF - signal). Based on the position of the tags in the interrogation zone, their response signals have unique delays and each creates a different beat frequency signal in the IF - signal. A filter bank is used to filter out different beat frequency signals from the combined IF-signal. In the second level, each beat frequency signal is Hilbert transformed to create the analytical signal. Then their magnitude and phase contents are extracted for data recovery and identification. <br> A novel chipless RFID tag localisation technique based on trilateration and Linear Least Square Approximation is proposed. This method uses a unique signal conditioning method for locating the tag’s position. The mathematical modelling of the chipless RFID system with three transceivers of a smart reader and multiple tags have been carried out, and different arbitrary tag positions are estimated. The algorithm has been validated through extensive simulation and laboratory experiment. Excellent performance within a circular interrogation zone of 1.2 meters of diameter with a transmitter power of 1 mW is obtained. With an extended transmitted power and multiple-reader configuration, the read range can be extended to a warehouse scenario. Finally, a smart reader configured with the developed anti-collision, data recovery and localisation methods is proposed. <br> With the recent interests of chipless RFID implementations in supply chain management and smart packaging from industry, the research has special significance. Therefore, this research has opened up a new horizon in the industrial applications of the chipless RFID system. The reader configured with the signal processing algorithms will facilitate multi-fold benefits for the Chipless RFID system in the new millennium.