Antenna Design for On-Skin UHF and 5G RFID Tags

This thesis presents RFID solutions for healthcare applications, using the battery-less (passive) communication link, in an attempt to provide medical facilities and individuals alike unrestricted access to well-being information. Through this technology, improvements can be made in early detection and illness prevention, as well as tracking and analysing recovery progress. To achieve this goal, an RFID tag must be designed to function on the body, a challenging task owing to the difficult electro-magnetic (EM) properties and variability of the human body. In discussing the challenges of the communication link, the first step is to consider dedicated frequency bands allocated for their controlled operation in public spaces, which for long-range RFID communication has been predominantly UHF (860 MHz). This wavelength parameter of the communication link is important as it has implications on the size and structure of the antenna to provide an efficient communication link. To this effect, this thesis has also considered the possibility of higher frequency 5G bands for RFID to potentially expand into, in order to reduce the operational wavelength, but also incorporate the many desirable qualities of a 5G network, foremost being its fast data rate, low-latency, and wide availability. The thesis is organised as to initially introduce RFID technology, discuss the current state of research around designing RFID tags for placement on the body. Going on to introduce a Directional Discontinuity Ring Radiator (DDRR) antenna as a novel application in the UHF RFID tag system for live streaming data, presenting 1.2 m range of consistent streaming, then up to 3.6 m maximum read range with dropouts. The thesis will then go into the design process for 5G RFID, adopting the grid-array antenna for its simple structure, high gain for the on-body environment, and potential for improved breathability. Since no RFID IC packages exist for 5G, and creating comparable circuitry is into itself a challenge, technological assumptions are taken from UHF to assess the quality these antennas obtain. The studies found the low-end frequency band for 5G (3.6 GHz) is comparable to UHF in terms of achievable radiation performance, but suffers the same structural limitations as UHF antennas, suggesting higher frequency 5G bands are required to produce a high performing epidermal antenna.