Dual band antenna for radio frequency identification applications

Abstract

Radio Frequency Identification (RFID) has the highest growth of applications system and is the most interesting field of research in communication technology. RFID systems have been implemented in various applications such as Electronic Toll Collection (ETC) and monitoring systems for railway stations. One of the ETC applications is the Touch & GO system that uses the Short Range RFID (SRRFID) technology. This technology benefits users as they are able to pay their toll automatically by passing through the toll gate without queuing for a long time. On the other hand, the monitoring system for railway stations uses the Long Range RFID (LRRFID) technology. Railway employees use this technology to monitor locations and automatically control the speed of trains from the railway station. Applications of LRRFID technology are meant for high-end users thus this technology has a higher marketability value as compared to SRRFID. Generally, LRRFID uses: (i) Ultra High Frequency (UHF) band and (ii) Industrial, Scientific and Medical (ISM) band. Both these bands can be applied using a single RFID multipurpose application reader. For this application, a multiband antenna is needed to fulfill the dual application. The aim of this research project is to develop a dual band antenna design operating the UHF and ISM bands having linear and circular polarization capabilities. A square patch antenna is selected as the basic design and modifications on the radiating patch were conducted using Computer System Technology (CST). The simulation from the CST resulted in development of dual band diamond shaped linear polarized antenna. The newly developed antenna has good return loss for frequencies in both bands. To enhance the quality of propagation of this antenna, a pair of slots was introduced to the radiating patch which transformed the proposed antenna to become a circular polarization antenna. Both antennas had air gap introduced between dielectric substrate layer and ground plane to boost the gain and efficiency of the antennas. The developed antennas have good gains, approximately 7~9 dBi and antenna efficiency is about 85~95%.