Passive UHF RFID with ferrite electromagnetic band gap (EBG) material for metal objects tracking

Passive UHF (ultra high frequency) RFID (radio frequency identification) is a promising technology for products tracking in logistics or routing packages in supply chain. However, passive UHF RFID tag suffers a lot when it is placed on conductive plane or water surface. Many designs like microstrip antenna and ferrite antenna have been used to solve this metal-water problem. But their use is limited by narrow bandwidth and low antenna gain. The electromagnetic band gap (EBG) material which exhibits a unique forbidden band gap at certain frequency offers a potential solution to solve the problem of backside objects effects. Previous research paper indicated that the dipole RFID antenna above three-layer mushroom like EBG material exhibited a good antenna gain and long read range. However, the complicated structure and high material cost greatly limit the application of tag. In this paper, we developed a new type of EBG material which uses ferrite film to reduce size and lower forbidden frequency. A commercial ferrite film which has a high permeability is applied to form two-layer mushroom like EBG material for UHF RFID. This two-layer mushroom like EBG material is a two-layer structure with a ground plane. The design of EBG material for UHF RFID which operates at 915 MHz was discussed in this paper. An EBG tag on metal with a gain of 7 dBi was achieved in simulation. The simulation results showed that the RFID tag still could be read on EBG substrate with a good gain (~7 dBi).