Radiated magnetic field of a low-frequency ferrite rod antenna

The frequency range below 135kHz is preferred for inductively coupled radio frequency identification (RFID) systems. At low frequency, the magnetic field coupling between reader and transponder can be increased by using a ferrite core transponder antenna. In this paper, the magnetic field pattern of such a device is investigated. A semi-numerical procedure is presented, how to calculate the magnetic fields resulting from coil and core with avoidance of virtual boundaries. Consequently, calculations at short as well as at large distances can be conducted with high accuracy and minimum computational expense. The model is finally verified by measurements and further simulation based on finite element method (FEM).