UHF-band RFID reader front-end architecture using ring-hybrid for near-field applications

In this paper, we present an antenna front-end architecture of UHF RFID reader dedicated for the near field applications. For the TX-RX isolation, the presented architecture adopts the sum-difference hybrid scheme which operates as a difference mode (or balun) and common-mode for TX and RX operations, respectively. The validity of the proposed architecture is demonstrated by applying to the smart shelf which identifies the books with UHF-tags. Compared with the conventional architecture using a directional coupler or a circulator, the test result shows the enhanced performance in sensitivity and multi-tagging ability.