Effect of the substrate, metal-line and surface material on the performance of RFID tag antenna

The radio frequency identification (RFID) is being used widely in various environments such as stores, factories, security systems and transportation cards, etc. A great deal of research has been reported on the development of tag antennas, but the effects of the substrates and metal-lines on the performance of a tag antenna have not been studied in detail. In addition, there have been few studies on the performance degradation of a tag depending on the target´s surface material to which the tag antenna is attached. In this paper, we examine how the characteristics of a tag antenna are altered by the substrate and metal-line materials. A simple tag antenna with the meander line radiator and T-matching network is optimized using Pareto genetic algorithm (PGA) to guarantee the maximum performance under variety of conditions. We then observe the effects of various targets´ surface materials on the performance degradations such as the readable range, the radiation efficiency and the shift in the resonant frequency.