A Dual-Resonant Microstrip Antenna for Paperboard in the Cold Chain

Passive UHF RFID tags have proved to be useful to serialize and automate tracking of goods through the supply chain, and the application of RFID to the cold chain is especially useful, where food safety and product quality are of special concern. The environment in the cold chain provides unique challenges to RFID tags, where water-based contents are the norm, and moisture and humidity can range widely. In this paper, we present a novel approach to addressing these challenges: using a microstrip antenna that uses the cardboard as the substrate. This introduces a new problem, namely that the wide variation in the dielectric properties of the cardboard makes it difficult to use traditional microstrip antennas. In this paper, we show a novel antenna structure and matching circuit that overcomes these challenges. The resulting design provides nearly uniform level of performance regardless of content and moisture condition. The antenna is readily manufacturable using traditional inlay manufacturing techniques.