A dipole-coupled metal-mountable UHF RFID antenna based on a vertical loop structure

This paper presents a novel UHF RFID tag antenna with metal-mount capability, broadband characteristics, and frequency controllability. To achieve anti-metal performance, we explore a vertical loop structure as the main radiator, with slots for frequency adjustment and layout flexibility. The antenna operates based on a hybrid magnetic–electric mode interaction mechanism, in which the vertical loop provides a magnetic-dipole-dominated radiation mode. Furthermore, asymmetric resonant dipole patches are loaded on both sides of the center feed line to introduce an auxiliary electric mode and broaden the operating bandwidth. This structural-level mode and coupling engineering enables independent control of the center frequency while maintaining wideband impedance matching. The proposed antenna has a compact size of dollar sign 0.1951 lamda times 0.128 lamda times 0.0051 lamda dollar sign 0.1951λ ×0.128λ ×0.0051 λ $ 0.1951 λ × 0.128 λ × 0.0051 λ $ , with the main radiation lobe concentrated within 60 dollar sign ring dollar sign ∘ $ ∘ $ from the zenith. By mounting on a dollar sign 100 times 100 times 2 mm 3 dollar sign 100×100×2\,mm³ $ 100 × 100 × 2 m m 3 $ copper plate, it achieves a maximum read range of 7.32 m, which demonstrates the good adaptability for UHF RFID tagging on metal surfaces.