A Multi-Antenna RAIN RFID Sensing Architecture for Pharmaceutical Climatic Chambers

Ensuring precise, in-package monitoring of temperature and relative humidity is fundamental for evaluating drug degradation processes during pharmaceutical Accelerated Predictive Stability (APS) studies. To this purpose battery-less, wireless probe sensors based on Ultra-High Frequency (UHF) Radio Frequency Identification (RAIN RFID) are emerging as innovative solutions for seamless monitoring of the micro-environment inside pharmaceutical packaging. However, APS studies are carried out inside metallic stability chambers that, being reflective, pose significant challenges for RF signal, often leading to reading coverage gaps and inconsistent data. This paper introduces a systematic experimental methodology for designing and validating an optimized multi-antenna RAIN RFID reading architecture for equipping a stability chamber to achieve approximately 100% reading coverage regardless of sensors orientations and positions. By experimentally refining the antenna type, number, and placement, as well as the interrogation power, the proposed methodology reliably overcomes electromagnetic interference. The results underscore the feasibility of robust, high-fidelity data collection via RAIN RFID passive sensors in APS scenarios as finally verified through an extended test for long-term monitoring of temperature and humidity within sealed pharmaceutical containers.