Low Profile Separable Rfid Tag Antenna Design For Variable Range Applications

The paper describes a novel passive tag design for RFID applications. The passive tag antenna has two separable parts, which are the feeding loop and the radiating element implemented at two different layers. Energy is efficiently coupled between these two parts when they overlap within designated positions. For demonstration purpose, the overall tag design is realized on a card (credit card size), and a card-holder, with the feeding loop embedded in the card and with the radiating element embedded in the card-holder. The key features of the tag design are i) the intended short read range of millimeter-to centimeter-level when the card is stand alone, and ii) the regular long read range of meter-level when the card is coupled with the card holder. With this distinctive characteristic, a card with a unique tag ID can be issued to a single person, on a one-to-one basis, for different read range access requirements in different situations, e.g. office gate access vs car park gate access of a single person to go in and out of a premises using the same access card, near-field payment vs road toll payment using the same payment card. Therefore, unnecessary false-read can be minimized and no multiple cards (different tag IDs), with different read ranges, are needed for the same person. A PCT patent of such design has been filed in Sept 2015 for licensing. A few hundred of proof-of-concept prototypes have been fabricated recently for field trials.