Low-Cost Electromagnetic Tagging: Design and Implementation

Several implementations of chipless RFID (Radio Frequency Identification) tags are presented and discussed as low-cost alternatives to chip-based RFID tags and sensors. An overview of present-day near-field electromagnetic tagging is presented, including both chipbased and chipless technologies with associated costs. As a candidate for low-cost ID tags, a design theory and implementation is presented for multiply-resonant planar metal structures. This theory includes a circuit model, a phenomenological model, and a framework for tuning the resonant frequencies as a function of geometrical and material properties. A novel physical geometry, a tree-like spiral structure, is proposed as a design that increases the number of resonances per unit area in a planar structure relative to the present day state-of-the-art. In addition to identification, it is shown how several chipless tags can also be designed to function as sensors. Several examples are discussed in detail, including: 1) a family of thermal sensor tags employing magnetic materials and 2) a family of sensor tags (to sense pressure, humidity, and pH) based on planar resonator structures. The latter section of the dissertation describes the evolution of my work in developing the necessary (and low-cost) instrumentation to support these new varieties of tag technologies, ranging from a $500 frequency-agile reader to a $5 reader for toy applications. A summary of emerging technologies and promising directions for electromagnetic tagging is also presented. Thesis Supervisor: Neil Gershenfeld, Associate Professor of Media Arts and Sciences