Fractal dipoles as meander line antennas for passive UHF RFID tags

In this paper, two fractal dipole antennas has been designed and optimized for passive RFID tags at 900 MHz, one based on the 3^rd iteration of a modified Koch fractal curve and the other is based on the 3^rd iteration of the proposed fractal curve. The designed fractal dipoles have been simulated using IE3D simulator based on Method of Moments (MOM). The simulation showed that the modified Koch fractal dipole has better radiation characteristics and longer read range than the proposed fractal dipole antenna. The two antennas are fabricated using PCB technology and examined in anechoic chamber. The experimental results showed a good agreement with the simulation. The effect of different materials attached to the fabricated antennas is examined.

1. Introduction

Radio Frequency Identification (RFID) is a rapidly developing technology which uses RF signals for automatic identification of objects. RFID system generally consists of three components: 1) a small electronic data carrying device called a transponder or tag that is attached to the item to be identified, 2) a reader that communicates with the tag using radio frequency signals, and 3) a host data processing system that contains the information of the identified item and distributes the information between other remote data processing systems [1]. A typical passive RFID tag consists of an antenna and RFID chip. RFID tags can be active (with battery) or passive (without battery). In particular passive UHF (860–960) MHz tags represent a near optimal combination of cost and performance [2].