A Smart RFID Gate System for Moving Direction Discrimination Based on a Reconfigurable Circularly Polarized Antenna

Radio frequency identification (RFID) has been xtensively applied in e-commerce and logistics, significantly enhancing the level of management intelligence and efficiency, particularly in the real-time and automated tracking of commodities. This paper proposes a smart RFID gate system for access control utilizing a reconfigurable circularly polarized (CP) antenna with a fixed installation, which greatly simplifies the system architecture and improves the detection efficiency. The discrimination gate system comprises two primary components: a reconfigurable RFID CP antenna and a hardware control platform for autonomous data extraction and processing. The designed reconfigurable CP antenna functions in the frequency range of 805 to 1010 MHz with stable radiation gain and switchable polarization modes, which enables the discrimination of tag movement direction at the detection gate by examining the variation trend of ΔRSSI values from two orthogonal CP modes. To ensure the accuracy and effectiveness of detection results, an automated decision program has been developed, capable of determining door location and tag movement direction by fitting detected RSSI values and analyzing variation trend of ΔRSSI. Theoretical simulations and experimental validations have been performed to examine the proposed detection approach, confirming its feasibility and significant potential for applications in intelligent logistics management.