Platform-tolerant RFID tag antenna

Abstract

The radio-frequency identification (RFID) has gained much interest in recent years, and its applications in many service industries have become widespread. This is because contactless transfer of data between reader and tag in identifying objects is more flexible than when a mechanical contact is used in automatic identification systems. The RFID has many attractive advantages over the traditional barcodes technology, such as its long read range, portable database, multiple read/write operation, and non-line-of-sight tracking capability. In this dissertation, several slotted-copper-trace (SCT) antennas and platform-tolerant RFID tag antennas are analyzed and presented. The work can be divided into two parts, which include the design and analysis of the stand-alone SCT antennas and RFID tag antennas. In the first part, the fundamental characteristics of an O-, R-, and OR-shaped SCT antenna are investigated. The return loss, current distribution, efficiency, and radiation patterns of the antennas are analyzed and studied. Parameters that affect the resonance frequency of the antenna are determined. Next, the proposed OR-shaped SCT antenna is used to design a new RFID tag antenna. The tag antenna consists of a radiating ORshaped SCT, a modified inductive feed, and a microchip. A ground plane is used in the design to make the tag antenna platform-tolerant. The input impedance, current distribution, percentage power transfer to the tag, and read range of the tag antenna are investigated. In particular, the differential radar cross section (DRCS), which determines the power of the modulated backscattered signal of the tag, is also studied. A parametric study of the RFID tag antenna was also carried out to show that the input resistance and reactance can basically be tuned independently. In the second part, a dual-function platform-tolerant RFID tag antenna using a modified I-shaped SCT and two Y-shaped stubs is proposed. The SCT functions simultaneously as an antenna and a radiating element of the RFID tag. The return loss, antenna efficiency, DRCS, read range, radiation pattern, and parametric studies of the tag antenna are investigated. The characteristics of the proposed antennas were simulated by using Zealand IE3D software, and the results were found to agree reasonably well with the measurements.

Date of Award	2 Oct 2008
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kwok Wa LEUNG (Supervisor)