Readers for frequency signature-based chipless RFID tags
thesisposted on 01.03.2017, 00:01 by Koswatta, Randika Vishwajith
Radio Frequency Identification (RFID) systems are currently a major research area globally. Most of the RFID tags available in the market use application-specific integrated circuits (ASICs) which are expensive compared to other tagging techniques. RFID can only compete with, even and replace barcodes if they are made chipless and printed like the barcodes. Chipless RFID tags reduce the manufacturing costs and enable the use of the technology in high volume applications. Much research has been carried out on the development of chipless RFID tags. However, only a limited amount of work has been carried out on the development of chipless RFID readers. This thesis presents the design of three novel, very low-cost chipless RFID readers for reading spectral signature-based chipless RFID tags. Two of the readers use frequency domain-based techniques to decode data from the chipless tags. The Gen-1 reader is capable of detecting the features of amplitude and phase signature of a chipless RFID tag. The reader requires a calibration measurement. The detection process is more hardware-based and fewer signal processing techniques are used. The Gen-2 reader reconstructs the amplitude and phase responses using the signals received from the chipless RFID tags. The reader does not need a calibration measurement, which offers a major improvement over the predecessors. The voltage controlled oscillator (VCO) of the reader generates a linear chirp (swept) frequency interrogation signal. The Gen-2 reader is even lower-cost compared to the Gen-1 and has a simpler RF section. The detection process uses a Hilbert transform-based signal processing technique to re-construct the amplitude and phase responses of the chipless tag. The operation of both Gen-1 and Gen-2 readers are validated experimentally. The tag reading speed is hindered by the performance of the VCO and the number of data points required in frequency domain-based readers. A novel high-speed tag reading technique based on ultra-wideband RF pulses is proposed in this research. The proposed method is validated with simulations. The integrated reader is a complete system with an RF section, a digital section and a graphical user interface (GUI) and software interface. Most of the existing UWB antenna designs are not suitable for chipless RFID applications due to their low gain or physical size. Hence, in addition to the readers, a design of novel UWB antenna is also proposed in this research work to use with the readers. The antenna is compact and high gain and provides UWB operation with over 9 dB gain and 3.9-10 GHz operating frequency band. The unique features of the developed chipless RFID reader systems are (i) low cost, (ii) secure and (iii) remote and non-line of sight operability. The importance of these developments lies in the fact that they enable the development of low-cost chipless RFID systems comparable to other cheap tagging systems such as optical barcodes.