UHF RFID Reader Antenna Applications of Non-Conventional Radio-Frequency Materials

Abstract

Antennas are complicated passive devices, found in transceivers which transform the electrical signals into electromagnetic radiation in the form of propagating radio waves. While there is a wide range of antennas, this thesis focuses on designing and fabricating low-cost patch antennas from non-conventional radio frequency (RF) materials. Patch antennas are low profile, planar antennas commonly used in cellular communications (mobile phone and base station antennas), point-to-point link communications (MIMO, SCADA, etc.), UHF radio frequency identification (RFID) systems and other radio frequencies (RF) products. Patch antennas are very common and attractive due to their form factor and cost. They are typically designed and manufactured using virgin dielectric substrate and conductive materials that are produced in well-controlled environments. These virgin RF materials, e.g. Rogers printed circuit boards (PCB), polyolefin like polyethylene, polypropylene, etc., exhibit both well-known and uniform electrical properties, which greatly aid in the design and manufacturing of high-performance RF products. Conventional RF materials are usually considered for high-frequency applications due to their consistent and predictable RF properties. However, these conventional materials are expensive and are dumped as e-waste at the end of their products' lifespan. This research aims to design and fabricate a low cost yet robust patch antenna and array using commercially available non-conventional materials. Commercially available non-conventional materials include thermoplastic sheets, thermal insulation materials, recycled materials etc. They tend to lose their virginity due to the manufacturing process and/or impurities being introduced. This leads to changes in the electrical properties of the materials, which inevitably impact the performance of the products manufactured using these materials. Designing patch antennas from such non-conventional materials requires an in-depth study of the materials and their electrical properties mainly its dielectric constant parameter as a patch antenna constitutes a metal radiating element as a patch and a ground plane, fairly larger than the size of a patch separated by a dielectric. Moreover, the electrical properties may or may not remain unchanged between different samples of the same material, or even between different regions of the same sample, due to the less stringent manufacturing processes of recycled materials, and this research aims to mitigate their impacts on products' performance through novel and innovative design and manufacturing techniques. UHF RFID application is chosen to make reader antennas using non-conventional materials to meet the form, fit and functional requirements. Various antenna designs in different non-conventional RF substrates are designed at a low-cost. Wideband antenna design methodologies are adopted to handle the changes in resonant frequencies caused by changes in dielectric parameters of a non-conventional patch antenna and array. The outcome of this research potentially open doors in the telecommunication industry to manufacture robust, eco-friendly antennas from various forms of commercially available inexpensive raw, reground/recycled materials without compromising its performance through proper optimisation and compensation.