Miniature Dual-Band Tag Antennas via Stacked Integration of a Folded Dipole and Dual-Patch for Antimetal RFID

Metal cabinet environments, characterized by densely packed enclosures and strong multipath scattering, degrade read reliability for single-band UHF RFID systems. This paper introduces a miniature dual-band RFID tag antenna that incorporates anti-metal features through a stacked configuration. A folded dipole formed on lower layers serves the UHF band, and a dual-patch array on an upper layer covers the microwave band, both excited by a single inductively-coupled feed. This design reduces the antenna footprint from 170.0 × 140.0 mm2 to 76.0 × 33.5 mm2 (about an 89.3% decrease), meets chip impedances of 20 − j179 Ω at 915 MHz and 36 − j24 Ω at 2.45 GHz. Realized gains reach 1.2 dBi and 5.8 dBi on metal, with read ranges of 2.7 m (free space) and 7.8 m (on a 200 mm × 200 mm plate). Reliability tests in a server cabinet show that, under low power and high speed, 915 MHz drops to 48%, 2.45 GHz reaches 90%, and the dual-band setup sustains 100%, confirming the proposed design's robustness in confined metal-rich scenarios.