Wireless sensing systems based on passive UHF RFID technology for physical parameters measurement

  • Author / Creator
    Ahmad, Shaheen
  • Sensing and monitoring using the conventional microwave, optical, and waveguide
    methods have been the focus of many researchers for the past two decades. However,
    the limitations imposed by these techniques such as power inefficiency and the use
    of complex readout circuitries are the important challenges for their successful
    implementation in the internet of things (IoT) based applications, when widespread
    deployment of sensors is essential. This dissertation focuses on the design of a new
    type of sensing systems utilizing a battery-less UHF RFID technology with the
    capability of power efficient remote sensing, reduced sensing node complexity, and
    lower maintenance over time.
    Various capacitive interdigitated electrode (IDC) sensing elements were designed and
    evaluated for different sensing applications. The working principle is based on the
    capacitance variation of the sensing element due to the changes in the permittivity
    profile of the test medium that alter phase of the backscattered RFID signal. In order
    to use the high sensitivity advantages of the capacitive sensing element and the
    passive nature of the RFID technology; the designed IDC structures were integrated
    with a three-port RFID sensing architecture to develop a reliable non-contact passive
    remote sensing systems.
    In the next step the proposed passive wireless sensing system was practically tested
    for remote liquid level detection in a real-world scenario. The presented solution is a
    simple three-port sensing architecture without any internal power source at the
    sensing node; that transduces liquid level variations into corresponding capacitance change, that adds an additional phase delay to the input RFID signal. The phase
    variation of the backscattered signal is used to estimate the liquid level in real-time.
    Furthermore, this concept is expanded to the volume fraction analysis of a binary as
    well as multivariable mixtures by modifying the sensing element structure and
    utilizing the limited RFID frequency band while taking advantages of the multitemperature measurements. The proposed method was evaluated by exposing the
    sensor to various mixtures containing different ratios of oil, alcohol and water. The
    difference in the phase values of the backscattered signal observed as a result of
    measurements at a single frequency (927 MHz) and multi-temperatures is used to
    calculate the unknown volume concentrations of the three components in a mixture
    based on the unique permittivity profile of the test samples. The presented sensing
    techniques provide a new solution for powerless real-time remote measurement in a
    densely populated sensing environment.

  • Subjects / Keywords
  • Graduation date
    Spring 2023
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.