The Shielding-Effectiveness Based Magnetic Field Shielding Theory and Its Application in Mobile Payment Systems

In this paper, we firstly introduce theory of magnetic coupling. Then, the shielding-effectiveness based electromagnetic shielding theory is studied, and the effectiveness of shielding materials to the coupling process is analysed in mobile payment systems. Simulation results show that when the feed frequency is low, plastic and lithium cell cause almost no attenuation to the magnetic field. If a shielding material is common metal, the magnetic field intensity is reduced to 20%-70% of the original. In the low frequency condition, the time-varying magnetic field produced by the transmitting coil is very stable and can resist the external interference. A convenient simulation software to calculate magnetic field coupling with shielding materials is also developed.