Preliminary Study of Mutual Coupling Effect on a Passive RFID Antenna Array

The communication quality between an RFID tag and a reader in a RFID network is affected by several factors including the distance between a reader and a tag, orientation of the antennas, and scattering from neighbor tags. Some studies have analyzed those factors and their impact on a read-rate of RFID systems. However, they neglected the effect of a mutual coupling among neighbor tags. In this paper, we formulate the driving currents of a RFID antenna array considering the mutual impedance among tags. Afterwards, we both measure and simulate the mutual impedance for the used RFID tag that is Alien 9640 Squiggle Inlay and we compare the result with half wave dipoles which we construct. Simulation results show that current distribution on tags increases when compared with the case that mutual coupling is not considered among tags.