The influence of water content in hydrated superabsorbent polymer on dielectric properties, antenna radiated power, and RFID tag readability

The performance and stability of RFID systems in a supply chain relies on the readability of passive RFID transponders. This thesis presents research on correlation and influence of readability on passive RFID transponders and water content in products simulated by hydrated superabsorbent polymer (SAP).; High water absorbable SAP provided a wide range of simulation options, from 45% to 95% water. The dielectric property in terms of permittivity of the hydrated SAP samples was characterized and differentiated by S-parameter measurement using a HP8510C network analyzer with a WR340 waveguide. Moreover, radiated power measurement and a readability survey using AlienRTM 915 MHz squiggle RFID tags with the same SAP specimens were performed with an R&SRTM NRP-Z22 power sensor with LabVIEW RTM program and AlienRTM RFID Gateway software.; The research results showed that the weight percent of water content in saturated SAP affected permittivity. The dielectric constant, Re ( &egr;r) and water content have a nearly linear relationship. The loss factor, Im (&egr;r) showed complicated fluctuations and sudden declines in some frequency ranges. High water concentration in the SAP mixtures indicated high power loss and low readability. More than 75% water content in the samples usually attained near 0% readability. Reader antenna style, position and transponder orientation showed different influence on readability and power loss with the same saturated samples. This research shows that product content and packaging operations are challenges to successful implementation of RFID system in supply chain.