Design of RFID tag antenna matched to microchip impedance

Abstract

Radio Frequency Identification (RFID) is a rapidly developing wireless technology that utilizes electromagnetic waves for the automatic identification and tracking of objects. An RFID system composes of a tag, which is attached to an object and uses an antenna to communicate with a reader. This research work presents the design of microwave RFID tag antenna and dual-band antenna with a modified Minkowski fractal. A dual-band antenna with a modified Minkowski fractal was selected, due to its many attractive characteristics. This fractal geometry has space-filling properties that can be utilized to miniaturize antennas. In addition, the self-similarity properties of fractals make them especially suitable to design dual-band antennas. These proposed antennas are designed using the electromagnetic simulation software called CST for a passive RFID tag operating in the Microwave frequency band. A single band tag antenna was designed and simulated for 2.45GHz. A high gain (5.842dB), a good impedance matching with the microchip (-30.0 dB Return Loss) and a satisfactory read range performance (upto 5 m) was obtained. A Dual-band antenna with a modified Minkowski fractal has been designed, fabricated, and measured. The proposed antenna is fed by microstrip line, and it consists of modified Minkowski radiating element on the top layer and partial ground on the bottom layer. Simulated and measured performance results are presented for a modified Minkowski small size (2.3x3.0cm) fractal antenna. The measured result for return loss of the proposed antenna shows that the antenna has two operating frequency bandwidths namely, the lower frequency from 2.36-2.525GHz and the upper frequency from 5.735-5.89GHz. The measurement results showed good agreement with the simulation result. One approach of designing RFID tag is that the tag should be less sensitive to the various types of objects. The effects of obstacles on antenna's characteristics have been investigated by placing the tag antenna against a metallic, rubber, glass and wood surfaces. Simulation results show slight variations which is within tolerance range.