Small On-Metal Passive UHF RFID Transponders With Long Read Ranges

This paper presents two small wide-band passive on-metal ultra-high frequency (UHF) radio frequency identification (RFID) tags for on-metal applications. The first single resonant design is for long-range RFID applications, whereas the second dual-resonant design is targeted for wideband purposes. The dimensions of the single-resonant tag are 66 mm x 22.38 mm x 7.52 mm and the dual-resonant tag has dimensions of 40 mm x 20 mm x 8.22 mm. Both designs are free of external matching components, the second design utilizes dual-stub matching. Both designs are based on the planar inverted L antenna (PILA), in which the planar radiator is placed on top of the ground plane. The radiator printed circuit board (PCB) is supported by styrofoam in both designs. The read range results for both designs were obtained with 3.28 W effective isotropic radiated power (EIRP) when the tags operate in the passive mode. The first design achieves a measured reading distance of 15.2 m at 872 MHz. For the second design, the achieved maximum read range is 7.2 m, and a minimum read range of 3.0 m within 902 MHz - 958 MHz. Both tags are designed to operate in the passive mode. The used PCB substrate is the commercially available and widely used FR-4.