Model of the RFID Antenna Using the Solenoid Coil Surrounded by a Coaxial Ferrite Toroid

A new model of the radio frequency identification antenna using the solenoid coil, surrounded by a coaxial ferrite toroid, is proposed in this paper. The truncated region eigenfunction expansion method is adopted to derive the expressions of the magnetic vector potential. Besides, due to the low conductivity and high permeability of the ferrite, a convenient solution region division is introduced to avoid solving the transcendent eigenvalue equation caused by the end effect as usual. Numerical calculations are performed, and the results are in excellent agreement with those obtained from the finite-element method simulations.