Slotted Folded Patch Antenna With Double-T-slots for Platform-Insensitive UHF Tag Design

A compact folded patch antenna, which has a dimension of 42 mm × 50 mm × 1.6 mm (0.128λ × 0.152λ × 0.0049λ) is proposed. Multiple C-shaped slotlines are incorporated for tuning down the resonant frequency of the folded patch. A pair of double-T-slots, which acts as the impedance matching network, is etched at the center of the patch for achieving conjugate match between the antenna and the chip. By combining the analytical method and the particle swarm optimization algorithm, an equivalent circuit model is constructed for analyzing the impedance characteristics of the proposed tag antenna. With the use of 4 W EIRP, a maximum read distance of 11.5 m is achievable by placing the proposed tag antenna on a dielectric object. Also, the tag antenna is found to be able to reach ~5.2 m on metal. The operating frequency of the proposed tag antenna is very stable for both the dielectric and metallic objects, which is very desirable for practical applications.