Investigations on electromagnetic interference in wearable passive chipless RFID tag array

Abstract In this paper, a passive, chipless ${2 \times 2}$ RFID tag array designed on a thin polyimide substrate is proposed for a wearable application. The radiating element comprises a star-shaped multi-ring structure enclosed in a square folded split ring. Requirement of compactness in wearables gives rise to electromagnetic interference (EMI) due to close coupling between the tag elements, which deteriorates the performance of the RFID system and requires mitigation of the EMI. In the present work, the coupling is analyzed extensively for two separate cases: when all array elements are of the same size and when they are of two different sizes, to investigate both inbound and outbound EMI scenarios. The orientation of each tag element with specific configuration is examined to achieve minimum coupling and to gain a larger read range, an important parameter in the design of passive RFID tags. Furthermore, specific absorption rate analysis confirms the safety and suitability of the design for on-body applications. The prototype model of the proposed configuration is developed, measured, and compared with the simulation results. A good agreement between the simulation and measured results confirms its suitability for compact wearable applications.