AN INVESTIGATION OF NOVEL UHF MICROSTRIP FRACTAL PATCH ANTENNAE FOR AN RFID DOORWAY READER SYSTEM

The applications of Radio Frequency Identification (RFID) technology has expanded drastically after the arrival of data revolution and coming age of human-free industry: Industry 4.0. The focus has been reduction of installation costs by developing plug and play systems when transitioning from traditional manual-scan systems to fully automated systems with improved efficiency.

The main contributor to efficiency of an RFID system is the reader antenna. Microstrip patch antennae are found to be most suitable for RFID applications. Miniaturisation of the antenna without compromising its efficiency has been one of the central concerns in the last few decades. For fixed reader RFID antennae, maintaining enough gain while having the ability to read tags moving in any orientation and speed as well as blindspots when clustered together have been major challenges in the industry.

The work proposed in this thesis aims to design miniaturised novel modified fractal antennae suitable for an RFID doorway reader system, operating at UK’s RFID UHF band, 870MHz. The work proposed combines novel miniaturising and gain enhancement techniques to meet desired requirements. Fractal patterns are used to increase the electrical length of the antenna while maintaining its physical size and obtain multiband behaviour thus reading tags slightly off-tuned with the help of RFID reader’s Frequency hopping technique. Antennae are made on high dielectric constant substrates, RF60A for further miniaturisation. Several geometry techniques including copper wall construction and 90 degree delayed two port feeders are used for gain enhancement, narrow beamwidth and circular polarisation. CST Microwave Studio Suite simulations demonstrate that a commercially available directivity (5dBi) compared to market research and published research papers have been achieved. RFID testing on manufactured prototypes demonstrated that antenna designs are suitable for a fully automated doorway reader system to obtain 100% detection efficiency with precise manufacturing and fine tuning.