Wearable Passive RFID Tags in Advanced Applications: Detection Methods for RFID-Enabled Sensor Tags and RFID-based Localization
Hasani, Masoumeh (2018)
Tampere University of Technology
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The radio frequency identiﬁcation (RFID) is one of the many Automatic Identiﬁcation and Data Capture (AIDC) methods which use propagation of electromagnetic waves for sending and receiving information. RFID has become increasingly popular over recent years from simple items labeling to more complicated applications such as sensing and positioning. One of the most exciting research trends of today in the ﬁeld of RFID is the sensing capabilities oﬀered by passive RFID technology. The massive use of wireless sensors in ubiquitous sensing and Internet of things (IoT) increases the demand for low-power, low-cost and sensing-friendly wireless communication devices. The well-known features of passive RFID system such as power eﬃcient nature, the tiny size and easy implementation can overcome some major issues of the remote sensor systems. In addition, introducing new materials and advanced manufacturing technique for fabrication of RFID sensor tags, as well as introducing less complex detection techniques for collecting the data from the sensor nods, can add more values to RFID to be prominent and promising technology for sensing application. In this thesis, ﬁrst, we concentrate on using the passive ultra-high frequency (UHF) RFID tag in wireless sensing applications. As results of the research work presented in this thesis, the novel and low-cost manufacturing techniques, as well as innovative detection methods for RFID sensor tags, were introduced. For the ﬁrst time, taking advantage of the nonlinear behavior of the RFID chip impedance as a function of the incident power, a novel sensing method has been presented. The method presented in this work relies upon the detection of the backscattered response for two distinct transmitting power levels and then calculating the diﬀerence between these two responses. The nonlinearity of the chip causes a large variation of its impedance value and thus a large diﬀerence of RCS value enabling a reliable operability over diﬀerent measurement ranges. The detection methodologies presented in this work are suitable to be implemented in any kind of industrial environment that utilizes the RFID-enable wireless platform for sensing. Second, this thesis deals with a novel hybrid conﬁguration for indoor positioning, utilizing the RFID and wireless local area network (WLAN). It is shown that combination of power eﬃcient, cost-eﬀective and easy to be implemented RFID system with WLAN technology, improve the localization accuracy compared to pure RFID and pure WLAN location solutions. The presented conﬁguration based on the hybrid model can be expanded for the larger indoor area, as it has been presented in the results of research work. Overall, this thesis thus provides insights into the beneﬁt of using passive UHF RFID tags and sensors in a wide range of application from inventory control and intelligent packaging to health care and human positioning.
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