Low-cost inkjet-printed UHF RFID tag-based system for internet of things applications using characteristic modes

The radio frequency identification (RFID) has emerged Internet of Things (IoT) into the identification of things. This paper presents, a low-cost smart refrigerator system for future IoT applications. The proposed smart refrigerator is used for automatic billing and restoring of beverage metallic cans. The metallic cans can be restored by generating a product shortage alert message to a nearby retailer. To design a low-cost and low-profile tag antenna for metallic items is very challenging, especially when mass production is required for item-level tagging. Therefore, a novel ultrahigh frequency (UHF) RFID tag antenna is designed for metallic cans by exploiting the metallic structure as the main radiator. Applying characteristics mode analysis, we observed that some characteristic modes associated with the metallic structure could be exploited to radiate more effectively by placing a suitable inductive load. Moreover, a low cost, printed (using conductive ink) small loop integrated with meandered dipole used as an inductive load, which was also connected with RFID chip. The 3-dB bandwidth of the proposed tag covers the whole UHF band ranging from 860 to 960 MHz when embedded with metal cans. The measured read range of the RFID tag is more than 2.5 m in all directions to check the robustness of the proposed solution. To prove the concept, a case study was performed by placing the tagged metallic cans inside a refrigerator for automatic billing, 97.5% tags are read and billed successfully. This paper paves the way for tagging metallic bodies for tracking applications in domains ranging from consumer devices to infotainment solutions, which enlightens a vital aspect for the IoT.