Compact ZOR Patch Antenna With Embedded Meandered Lines for UHF RFID Tag Design on Metal Platform

For the first time, two sections of planar meandered lines are incorporated with a compact C-shaped patch structure for designing a zeroth-order tag antenna that can be applied on metallic platforms. The proposed antenna operates at a resonance frequency of 0.915 GHz, which falls within the US UHF RFID (0.902 - 0.928 GHz). The meandered lines can introduce sufficient inductances for enabling the zeroth-order resonance. Also, the line dimension can be adjusted to tune the tag resonant frequency effectively. An analysis of the antenna's characteristics was carried out through unit cell simulation. It has been found that the zeroth-order resonance can be successfully excited even with the inclusion of the microchip. The proposed tag antenna is compact ( $20\times 40\times 1.6$ mm3), and it has a broadside read pattern with a long distance of up to 11.29 m at EIRP 4 W. When tested on various metal objects, the proposed tag has demonstrated consistent read performances.