Confinement of the detection region is a critical issue for some important RFID applications, where the coarse location of the object is required along with its identification. In the UHF band, it is a challenge to confine antenna radiation to reasonably sharp interrogation volumes, <10 lambda(3),without resorting to physical barriers. This paper presents a novel approach for RFID reader radiating structures that self-confine tag detection to a desired volume, avoiding undesired readings outside the interrogation volume. The proposed solution simultaneously covers the three world-assigned RFID frequency subbands at UHF. To demonstrate the effectiveness of the solution, the proposed configuration was integrated into bookshelves, a conveyor belt system, and a proximity point reader. Together with an appropriate control application, these form the building blocks of a smart store with automatic inventorying and billing capability. The radiating structure concept was explored by full-wave simulations, and it was validated with both near-field measurements and with tag-reading scores. Short demonstration videos are available online.

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RFID; UHF antennas; microstrip antennas; RFID antennas; near-field UHF RFID; smart RFID reading surfaces

• Electrical Engineering, Electronic Engineering, Information Engineering - Engineering and Technology