RFID Antenna Near the Surface of Metal

Nowadays, RFID (radiofrequency identification) technology is becoming more and more popular. One critical problem is that most passive RFID tag can not be placed on metal objects because metallic surface changes its radiation pattern, input impedance, radiation efficiency and resonant frequency. Through detailed theoretical analysis, relationship between the distance to the metallic surface and the tag' s communication efficiency is deduced. Finite element method (FEM) is used to simulate the dependency of antenna efficiency on the distance of the plate. Experiments have also been carried out to verify the analysis and the simulation results. Finally, a recommended distance of RFID tag placed on metallic surface has been given.